Weird. I saw you replied from my phone yesterday, but now it's gone. Storm perhaps?
Anyway, now that I'm on a regular keyboard, I wanted to respond to your reply. Sounds like you did the right thing. We had an opportunity to play 15u ball(skipping 14u except for some fall play), but with transitioning to the 90 foot bases and BBCOR bats too, the older kids who would be turning 16 this summer would have run my 14 year old off the field. Arms too strong etc. Too much change all for one season. So, I get what you are saying. The puberty thing hits some kids way early and some very late. You have to do what is best for your own son.
The size of the fields are not an issue since he has a strong arm and adequate speed. However, his age/size/strength deficit as a late April 98 lb. 12 year old puts him at a disadvantage that is too large to overcome at the 13U Major/AAA level.
He's playing AA this year until his body develops. He's playing with his old T-Ball pals in our North Gwinnett community, and is having fun. He'll be one of those late bloomers, if he sticks with it.