He bails out of early pressure in situations where many quarterbacks would fine a receiver. He also bails out backward that traps him into usually only having the option to throw the ball away. When he can bail sideways, he does so and has had better success finding people. But he rarely finds good places to simply shift the pocket forward or to the side to free up open receivers. He's like Clausen. Except, despite being extremely athletic, his vision and feel for the pocket is so bad, he rarely gets to use that athleticism.
Tommy in all his immobility would likely have fewer sacks because he'd find receivers over the middle when pressure comes.