That's the whole point of The Confessions. The conversion of a man caught up in the cults of the day who prayed, "Give me purity and continence, but not yet" so that he would become a Saint and Doctor of the Church.
Could Augustine have overstated his case? Perhaps. He did it before with the Donatist controversy when he took "compel them to come to the feast" and used that to justify closing the Donatist churches by military intervention.
It's significant that Morgan is associated with both the Celtic Church and the Eastern Church, both out of the orthodox eastern rather than the Roman tradition.
It's significant that Morgan's case, when presented by Morgan, was affirmed. When presented by his opponents in his absence, he was castigated.
It is significant that Rome's overtures, with Augustine heading the delegation, were rebuffed by the Celtic Church.
You have added more: Augustine had a history of being heavy-handed militarily with the Donatists.