Can't be certain, but looked like Grant was negatively reacting to the whistle blown ON THE WAY DOWN from his jump...which even considering how crazy high that guy gets is still too quick a whistle, implying that the ref (probably just making a human mistake) assumed a foul on that play.
I guess there are two schools of thought here, that it should never be a foul because it was probably a clean block...OR, what likely happens is the officials "award" the offense that play for having out-positioned the defense on that particular play. Sort of like a PI penalty in football
Anyway, I'd be curious if your review of the replay shows a way-too-quick whistle on that play.
That said, I didn't agree with some folks on the chat that the refs were bad! or worse than any conference road game...thought we went through a funk and the truth is you really can't give D1 basketball players 18 wide open threes...they'll make a high %.