It’s all pretty much a had to be there situation. If the defender taps/pokes the shooter after the shot is released, probably a no call. If he kind of just taps him as a course of his body’s movement settling into a defensive position, it’s probably incidental as long as it didn’t interfere with the shot.
If, however, the defender is standing there and as the shooter goes up, the defender lift his hand, sticks out his finger and then pokes him in the belly button while the shooter is in the air, I would call the foul. What would be the proper mechanic for tickling?