I do think after making it a point of emphasis, the NCAA has completely dropped the ball on lane play and post play though I agree it is a much more difficult situation to referee - who initiates contact, who is pushing too hard against the other other player?
What has upset me all year is the lower body contact on shooters in the act of shooting near the basket where it displaces the player. It is happening a lot and seldom being called. Touch the shooters arm and it is a foul, displace the body by 12 inches and most of the time it is not.
Specific to rebounding it is a difficult situation - a blocking player and a blocked player will be leaning against each other to maintain their positions. If one player jumps before the other, it removes their base and they will naturally be displaced as they are no longer grounded. Generally the one who hasn't jumped maintains their balance and does not overly displace the jumper and no foul is called (and it shouldn't be.) And if the jumper is the taller player because the initial pressure was lower on their center of gravity and becomes lower still as they jump, there is more tendency to be 'submarined' by the shorter player - not just displaced but overbalanced/knocked off vertical. The general rule of thumb in the decision between 'over the back' vs. a displacement foul seems to be if the ball would naturally have fallen in a reasonably close position to the leaper it is not over the back, if they have had to reach far into the space above or in front of the displacer it is.
With a player like Stewart (and Stokes) who have a decent vertical and long arms it is harder to define that space and you see a lot of opposing coaches complain about non-calls of 'over the back' in Uconn games because of this. It is very much a judgement call and I think generally it has been called well - there are always a few disputable calls and non-calls, but I haven't seen a bad trend in the Uconn games or any game where I thought the refs were consistently miscalling the distinctions. Nor have I seen coaches or players disputing many of those calls during a game beyond the standard 'who me' kind of reaction to any foul.
On that particular play - there was certainly a lot of displacement that occurred, but I think the call was based more on where the rebound was coming down and the fact that Stewart was reaching far into the opponents natural space initially. Definitely a debatable foul, but one that there is probably no truly 'correct' call to make.