I feel you on that. Made a Athletic PF and I would box out every shot, be in position and get 2-4 boards a game.
I swear that the AI knows whether each shot is going in or not. You see them crashing the boards hard on every miss, and slacking/getting boxed out on every make. It's ridiculous that my 6'3 shooting guard is averaging 5+ boards a game and can get 15-20 if I really go for it while my 6'11 PF couldn't get upwards of 5 boards even when that's what I put most my effort towards. Had to delete that mycareer out of frustration.