+Athanasius, for example, as well as +John of Damascus, considered Didache to be canonical. But the Church didn't! So, while +Jerome was allowed to voice his opinion, he coud do so without condemnation as long as it was not stated as fact but as a theological opinion (theologoumena). As you mention, however (and this is crucial) he submitted to the wisdom and the Apostolic authoirty of the Church
That's the key difference between us and some Protestants... They submit only to themselves.
Regards