Billy hates lying to his friends , especially the ones on the Justice League but the only way he can keep being with the Justice League is to pretend he is an adult , even though his Shazam form looks more teenager barely young adult, he somehow has the team convinced he is a few thousand years old. ( Flash and GL’s fault they started a betting pool) and gossip went down hill from there, but hey least his identity is safe and full proof!
Least with John and Danny he can be himself, and learn magic as Billy instead of Shazam, cause his Shazam side already knows magic! But Billy doesn’t and he wants the slow process experience, John teaches him but makes sure he never dares touch anything Occult.
Billy sees it in his Uncle’s eyes whenever Billy does study something related to Occult magic but that’s only so he can identify it , NOT use it, John fears he might get to curious and warns him magic especially the dark arts, always come with prices.