[JRutledge]

You might be waiving off a shot to signify that your foul or your violation has nothing to do with a shot. Your signal helps make it clear that you have to shot. The ball is already dead by the time you blow your whistle, so waving off the basket might be to clarify that you have no shot and any basket that goes in is not going to count. Because if you do not do that, any action when the ball is dead because of foul or violation, you might get asked by the table or your partners, "did the basket count?" To me it is always good to use your signals just like your voice. You might have to in some cases to signal something at the table. But listen to your assignors.

Peace