It's interesting. He's certainly not finding all the "GM moves", so an 1100 should be able to play to a similar level. But he's still able to increase elo by 100 within 2 hours.

​@RG001100 That is probably because while there are habits moves, there are so many possibilities. He's not playing tactics every move, and it's those moves that aren't tactics that will be harder for lower rated players to choose between. He also sees every tactic which isn't necessarily easy for low rated players. So him being a GM certainly helps. He also remembers every tactic he's seen. Which is necessary to improve, but difficult to start doing.