or reaching from directly behind to poke a ball loose from a dribbler. I know refs that theorize it really isn't physically possible to get the ball clean in those situations without making contact to gain an advantage. I kind of agree unless in the "over the back" case, the difference in height is exaggerated or the point of the ball at contact is already over the shorter player's head with inside position. I agree in general when a shorter player inside goes straight up for the ball and loses it to a taller player from behind (hello Kentucky Wildcats), there is almost always significant contact used to gain the advantage.
Similar with blocked shots. How many blocks are really clean? How many times do you see a fantastic block that sends the shooter flying because of body contact? Is it really that hard to block a shot if you are allowed to run through the shooter?