After growing up and maturing some I'm actually a little embarrassed to admit this but when I played in college we had a "pick off" move that according to the rule above was a balk but we were NEVER called on it. Runner on first or second and RHP totally ignores the runner after getting ball and walking around mound once. Gets onto the rubber right foot then left foot. Takes the sign and still hasn't looked at the runner. He "starts" his deliver by raising his hands up and stepping back with his right foot and not his left foot (remember RHP). So he's actually disengaged the rubber but has done so by simulating the pitch. Runner sees this and takes off for next base and we get him out. Not a single umpire nor opposing coach said anything about this but this was early 90's so not sure if the rule existed then or not but my guess is it did.
I've seen that move used as low as 11u. Some umpires call it a balk and some do not. If the umpire seems inexperienced some kids will do it.