There’s not a college in American that won’t see AB as rigor.
If the teachers think AB is the proper course, he should not jump ahead.
Typically, if you can take one or the other, they’ll place you where you belong.
It’s unlikely his college outlook will be vastly different from having AB vs. BC.
Math is foundational - and AB is plenty rigorous.
If they say he’s ready for BC, it’s one thing - but if he’s slated for AB, that’s fantastic as well. No need to jump.
Good luck.