Well let's be honest, how do you know they wouldn't have left the crease if the bowler pretended to bowl it and waited for them which has been what happened in most of the recent mankad controversies
Peter Della Penna also done an analysis showing the ground being stolen tended to depend on who was at the other end and how far into the over it was.
Keemo Paul doesn't even go into his action during his run-up so not sure he can been seen as having pretended to bowl.
Maybe Kohli or other batters would be out of their crease if bowlers pretended to mankad but its not the reason that many of the batters getting mankaded now are getting dismissed.