In the Catholic Encyclopedia article I linked in 280 a distinction is drawn between pre-Augustinian thought, St. Augustine's teaching, and post-Augistinian, particularly Thomist, teaching on Limbo. Do you think that the article is incorrect, or that the distinction that exists is covered by your caveat "essentially accepts"?
Church teaching on the nature of Limbo is speculative. Teaching on Original Sin is dogmatic.
Obviously, theological speculation about Limbo can change and is the subject of disagreement. One need only compare the lot of those dying in Original Sin alone in the Summa of St. Thomas and the Divine Comedy of Dante.
The theology of Original Sin is not subject to change, nor did it originate in St. Augustine. The nature of Original Sin is perfectly clear in the writings of Origen and St. Cyprian, 150 years before St. Augustine.
The "essentially accepts" refers to some of St. Augustine's speculations on the roles of grace and free will in the process of justification, some of his theorizings on the nature of predestination and reprobation, etc. It is to be expected that St. Augustine expressed himself in more than one way, and perhaps not in the exact manner the Church ultimately adopted as a guidepost, since he was the one who more than all the others combined, worked through these issues in the struggle with Pelagian heresy, sometimes coming back to change or tweak his position, as in his book of Retractions.