Interesting take from Hardwick on Tyrone.
He says his aerobic capacity is very poor. This is why they use Griff in the ruck. If they try Tyrone, he is buggered and can't run.
That is why he stays forward and Griff has to be the jack of all trades - forward, ruck/follower.
So he knows his limitations but because he kicks goals and provides a tall target, he gets a game.
Source: Hardwick
Edit: McBean doesn't provide a good marking target at the moment. If he did he'd get a game. Hardwick says he plays too much like a small and lacks intensity.