Some folks have denounced the note as a forgery. However, no reason for the forgery has been adduced. None of the associates of this rabbi are Christians, and there does not appear to be any way for Christians somehow to infiltrate the group of "ultra-Orthodox" (per the article) Jews and plant this note. I suppose an enemy of his could by trying to suggest that he had secretly converted to or compromised with Christianity, but there would seem to be much easier ways of trying do this.
What does this confirm? Not that much. One is tempted to conclude that even an unbeliever like this rabbi can come to see much truth about the Messiah from careful study of the Old Testament, and the article highlights a number of points where we would say that this rabbi got it right (as well as a few where he was way off the mark). One may even say that this name of the Messiah is found in the Old Testament forshadowed in at least two ways. Justin Martyr explains one way:
Justin: Moreover, in the book of Exodus we have also perceived that the name of God Himself which, He says, was not revealed to Abraham or to Jacob, was Jesus, and was declared mysteriously through Moses. Thus it is written: 'And the Lord spoke to Moses, Say to this people, Behold, I send My angel before your face, to keep you in the way, to bring you into the land which I have prepared for you. Give heed to Him, and obey Him; do not disobey Him. For He will not draw back from you; for My name is in Him.' [Exodus 23:20-21] Now understand that He who led your fathers into the land is called by this name Jesus, and first called Auses [Numbers 13:16]. (Oshea). For if you shall understand this, you shall likewise perceive that the name of Him who said to Moses, 'for My name is in Him,' was Jesus. For, indeed, He was also called Israel, and Jacob's name was changed to this also. Now Isaiah shows that those prophets who are sent to publish tidings from God are called His angels and apostles. For Isaiah says in a certain place, 'Send me.' Isaiah 6:8 And that the prophet whose name was changed, Jesus [Joshua], was strong and great, is manifest to all. If, then, we know that God revealed Himself in so many forms to Abraham, and to Jacob, and to Moses, how are we at a loss, and do not believe that, according to the will of the Father of all things, it was possible for Him to be born man of the Virgin, especially after we have such Scriptures, from which it can be plainly perceived that He became so according to the will of the Father?- Justin Martyr, Dialog with Trypho, Chapter 75 (source)
And he also explains another way:
Justin: But you ought to believe Zechariah when he shows in parable the mystery of Christ, and announces it obscurely. The following are his words: 'Rejoice, and be glad, O daughter of Zion: for, lo, I come, and I shall dwell in the midst of you, says the Lord. And many nations shall be added to the Lord in that day. And they shall be my people, and I will dwell in the midst of you; and they shall know that the Lord of hosts has sent me unto you. And the Lord shall inherit Judah his portion in the holy land, and He shall choose Jerusalem again. Let all flesh fear before the Lord, for He is raised up out of His holy clouds. And He showed me Jesus (Joshua) the high priest standing before the angel [of the Lord ]; and the devil stood at his right hand to resist him. And the Lord said to the devil, The Lord who has chosen Jerusalem rebuke you. Behold, is not this a brand plucked out of the fire?' [Zechariah 2:10-13, Zechariah 3:1-2]- Justin Martyr, Dialog with Trypho, Chapter 115 (source)
As Trypho was about to reply and contradict me, I said:
Wait and hear what I say first: for I am not to give the explanation which you suppose, as if there had been no priest of the name of Joshua (Jesus) in the land of Babylon, where your nation were prisoners. But even if I did, I have shown that if there was a priest named Joshua (Jesus) in your nation, yet the prophet had not seen him in his revelation, just as he had not seen either the devil or the angel of the Lord by eyesight, and in his waking condition, but in a trance, at the time when the revelation was made to him. But I now say, that as [Scripture] said that the Son of Nave (Nun) by the name Jesus (Joshua) wrought powerful works and exploits which proclaimed beforehand what would be performed by our Lord; so I proceed now to show that the revelation made among your people in Babylon in the days of Jesus (Joshua) the priest, was an announcement of the things to be accomplished by our Priest, who is God, and Christ the Son of God the Father of all.
Now, don't get me wrong - Justin's arguments (especially the first one) are not very compelling without the further revelation provided by Jesus himself. Nevertheless, these and other passages may make clear to even an unbelieving rabbi who studies enough, that the name of the Messiah was to be Jesus. Furthermore, one might also observe that names are picked for their significance, not simply for their ephony. Thus, the name "Jesus" which means "Savior" is not a surprising name for the Messiah, given the Messiah's salvific role.
In fact, we are told that this is the reason for the name:
Matthew 1:21 And she shall bring forth a son, and thou shalt call his name JESUS: for he shall save his people from their sins.
Which is indirectly a proof of the divinity of Jesus:
Zechariah 9:16 And the LORD their God shall save them in that day as the flock of his people: for they shall be as the stones of a crown, lifted up as an ensign upon his land.
Jesus is the Saviour because Jesus is God. We are His people and the sheep of his pasture:
Psalm 79:13 So we thy people and sheep of thy pasture will give thee thanks for ever: we will shew forth thy praise to all generations.
Psalm 95:7 For he is our God; and we are the people of his pasture, and the sheep of his hand. To day if ye will hear his voice,
Psalm 100:3 Know ye that the LORD he is God: it is he that hath made us, and not we ourselves; we are his people, and the sheep of his pasture.
For this shepherd is Jesus, who was prophesied by the prophets:
Zechariah 13:7 Awake, O sword, against my shepherd, and against the man that is my fellow, saith the LORD of hosts: smite the shepherd, and the sheep shall be scattered: and I will turn mine hand upon the little ones.
The shepherd will be smitten and the sheep will be scattered, but there will also be a salvation and ingathering of the sheep:
Ezekiel 34:12 As a shepherd seeketh out his flock in the day that he is among his sheep that are scattered; so will I seek out my sheep, and will deliver them out of all places where they have been scattered in the cloudy and dark day.
We know that Jesus fulfilled these prophecies:
Matthew 26:31 Then saith Jesus unto them, All ye shall be offended because of me this night: for it is written, I will smite the shepherd, and the sheep of the flock shall be scattered abroad.
Mark 14:27 And Jesus saith unto them, All ye shall be offended because of me this night: for it is written, I will smite the shepherd, and the sheep shall be scattered.
John 10:11 I am the good shepherd: the good shepherd giveth his life for the sheep.
And while there are others who can be viewed as "shepherds" in a lesser sense, Jesus is the one unique Great Shepherd:
Hebrew 13:20 Now the God of peace, that brought again from the dead our Lord Jesus, that great shepherd of the sheep, through the blood of the everlasting covenant,
1 Peter 2:25 For ye were as sheep going astray; but are now returned unto the Shepherd and Bishop of your souls.
And do not forget - our Shepherd is Jehovah, the LORD:
Psalm 23:1 (A Psalm of David.) The LORD is my shepherd; I shall not want.
Jeremiah 31:10 Hear the word of the LORD, O ye nations, and declare it in the isles afar off, and say, He that scattered Israel will gather him, and keep him, as a shepherd doth his flock.
There are so many such proofs that I will not now burden you with all of them. Suffice that those who truly follow the Old Testament will follow Jesus:
John 5:46 For had ye believed Moses, ye would have believed me: for he wrote of me.
And those who study them are studying Christ:
Luke 24:44 And he said unto them, These are the words which I spake unto you, while I was yet with you, that all things must be fulfilled, which were written in the law of Moses, and in the prophets, and in the psalms, concerning me.
And consequently, we (and especially Jews) are exhorted to search the Scriptures and to find Jesus there:
John 5:39 Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.
We have no strong evidence that this particular rabbi trusted in the already-come Messiah Jesus, but may God give others who read his works grace to see that Jesus is the Messiah, the very Son of God who is the Shepherd of Israel and the Judge of All the Earth, who also will come again to judge the Earth on the last day. (link to article - but see this previous article about the dangers of religious journal)