Did Augustine Change his Mind on the Canon?

In his Revisions (aka Retractiones), Augustine offers a number of corrections to his previous work.  He is the only author that comes to mind as having engaged in such systematic self-criticism.  The recent translation of his works "The Works of Saint Augustine: A Translation for the 21st Century," uses the title "Revisions," while some others have used "Retractions."  Retractions is a more natural cognate, but Revisions is probably more accurate as an overall description of his work.

One of the revisions he proposes relates to his Two Books on Genesis Against the Manichaeans.  The citation is Revisions, First Book, 10 (9), section 3, he writes (p. ):

Again, I do not seem to have been correct in referring to what is written, Why are earth and ashes proud? (Sir 10:9), as prophetic words, because they are not read in the book of someone who we are certain ought to be called a prophet.

The reference is to what Augustine said in On Genesis: A Refutation of the Manichees, Book II, 5 (6) (trans. from the WSAT21 series, vol. I/13, p. 74):

When the soul was being watered by such a spring as that, it had not yet "cast out its innards" through pride. The beginning, you see, of man's pride is to apostatize from God (Sir 10:12); and since his swelling out through pride to exterior things has put a stop to his being watered from that interior spring, he is very properly jeered at by these words of the prophet, and told: What has earth and ashes to be proud of, since in its lifetime it has cast out its innards? (Sir 10:9).

Later on, in Revisions, Second Book, 4 (31), section 2, he writes (p. 113):

In the second book, concerning the author of the book that many call the Wisdom of Solomon, namely, that Jesus Sirach wrote it just as he did Ecclesiasticus, I afterwards learned that this was not as agreed upon as it was said to be by me, and in all probability the book's author is not discoverable.

When I said, "The authority of the Old Testament is confined within these forty-four books," I referred to the Old Testament according to the Church's customary way of speaking. The Apostle, however, seems to refer only to what was given on Mount Sinai as the Old Testament.

Finally, in Revisions, Second Book, 20 (47), he writes (p. 128):

In the first [book], then, it did not occur to me that what I said about the manna--that it tasted in each person's mouth as he himself wished it to-- could not be demonstrated by any text apart from the Book of Wisdom, which the Jews do not accept as having canonical authorship. 

The "first [book]" in question is found in Augustine's works as Letter 54, and the specific citation is Letter 54,3,4. (trans. from the WSAT21 series, Letter 54, p. 212)

It also serves as a comparison in that in the earlier people the manna tasted in the mouth of each one as the individual wanted, just as that sacrament by which the world is conquered has a different taste in the heart of each Christian.

What's particularly interesting here is that Augustine's original argument does not hinge on Jewish acceptance of his argument.  He's writing to Januaris and the section is dealing with the sacrament of the Lord's Supper. Why is Jewish acceptance relevant? The only answer staring us in the face is a tacit acknowledgment that Jerome is right about the canon.  Maybe the churches read and use Sirach and Wisdom, but they do not have full canonical status to establish doctrine.  Likewise, Wisdom is neither a book by Solomon (as originally thought by the North African councils) nor even a book by Jesus Ben Sira (as had been speculated).  Instead, it's a book of uncertain authorship, despite its obvious claims to be by Solomon.