i don't think you can characterize a bh grip by heel pad positioning like you can on a fh because a) small grip size he uses and b) he's not using his palm or heel pad to push the ball. he's whipping the racquet around and pulling it towards the ball with his shoulder and core. He's not pushing up against the racquet on the heel pad like you do on a fh. He has a large butt cap to keep the racquet from flying out of his hand because he's pulling the butt to the ball. The heel pad position on a 1hbh doesn't play a major a role as it does in a fh.
A grip is characterized by how the racquet is faced when you hold it. A racquet will be quite closed early in the takeback w/ an extreme grip. gasquet's is not.