Undercutting a shooter needs to be more consistently called; right now, like everything else, stars get away with too much. That move injured players.
Oh, there's a reason why it's not called. Coincidentally, it's the exact same reason why that ref called Harden's flop against Wesley (the one where he literally wasn't TOUCHED and he fish flopped on the ground holding his face like a bitch).
NBA refs are spectators. They like to see the shots, moves, dribbles, and dunks just like we do. The problem with that is you get caught up watching and forget to referee.
There is a cardinal rule that can catch 100% of these instances that must be followed:
Stay with the shooter. It's that fucking simple.
It's as simple as Dick and Jane.
See shooter jump (that's also the same time you determine if the shot is a 3 pointer). See shooter release. See shooter land. This takes less than 2.5 seconds.
Once that is done THEN you look (not at the shot) for pushes in the back on rebounds. Seeing the shot go in should only be a consequence of you looking for pushes in the back.
NBA referees are too busy looking at the shot going in.