[Adam]

If the defense commits illegal contact that could warrant a foul, you also have to determine whether there is an advantage gained. Consider this case:
A1 driving past B1 while B1 reaches in and hacks A1's non-dribbling elbow. A1 has B1 beat, and B1's contact had no effect on the advantage gained by A1. No foul. Let A1 have the layup. If they make it, you haven't taken away their advantage. If they miss, it isn't because of the contact before the shot.
It sounds like in the original play described here that there was no advantage gained by the contact.

I don't base my whistle on whether or not the shot goes in; it's whether or not the illegal contact results in a more difficult shot. I'm not comfortable with waiting to see if a shot goes in.