Dunk or Illegal Dribble

[NewNCref]

A1 comes dribbling down the court, wide open on a fast break. A1 throws the ball off the backboard (obviously not an attempt at a shot), catches it in the air, and dunks the ball.

Partner (a veteran official) makes no call. After the game, I ask him about the play, and he says it's perfectly legal. I ask about the possibility of an illegal dribble call, and he says since it's at their basket, it's okay.

Is this correct, and if so, NFHS rules citations or case plays would be greatly appreciated.