For some reason, no iPad had it. Maybe it becomes problematic on large screens, maybe the user experience degrades on large screens because of simple physics i.e the the strength needed for applying pressure becomes uncomfortable since it will act as a lever in the hands of the user?
Maybe the force the user can apply when iPad is on a table(no lever effect) and when is handheld(strong lever effect, user needs counterforce on the other end of the screen to achieve firm press) is far too different to reliably activate the gesture?