God becoming human wasn’t simply a thing that happened, it is proof of his nature to bend low, to speak in ways that we can understand, to wrap himself in coverings that make sense to us, and to give us an answer that we can understand to this exact question.
Mary, however, did not need to learn who he was. She knew exactly what his identity was from his first breath even if she had no idea how this God-child of hers would accomplish his mission.
The startling aspect of this notion is that if Jesus was fully human and “grew in wisdom” that means that his sinlessness wasn’t in that he always knew everything and had all the answers so much as that when he faced any decision, he always chose the right path, the godly path