Here's the video:
He (the defender) clearly is holding, but again, its within 5 yards of the LOS. So there is no holding foul.
Then he (the defender) LETS GO. That's when the ball is in the air. And then the defender knocks the ball down, WITHOUT making contact with the WR.
Now, you can't see exactly when the ball is in the air vs when he lets go of the WR. But its certainly not obvious either way, and the WR wasn't being touched at all when the ball arrived.
So again good NO call.