Touching the backboard is only a violation if it affects the shot.
"Vibrate the rim, net or backboard so as to cause the ball to make an unnatural bounce"
Section I—A Player Shall Not: Touch the ball or the basket ring when the ball is sitting or rolling on the ring and using the basket ring as its lower base or hang on the rim while the ball is passing through. EXCEPTION: If a player near his own basket has his hand legally in contact with the...
official.nba.com
In real time, it looked like he might have affected it, but in slo mo, the ball wasn't going to go in anyway.