Yeah there are way better hands to flat here and even if we have seen him open some suited Ax from here he still has 36 combos of AJ-AK and only 24 combos of suited Ax assuming he opens them 100% and we don't know this. Without initiative or position this is going to play badly and you'd be much better turning it into part of your 3 bet bluffing range having some blockers etc, provided he can fold to 3 bets. I'd rather flat JTs T9s etc.