Let's turn that argument around. If I had hit the ball that was sitting on top of the net cord and followed the ball to net to begin to blow it to the opposite side, it would have to be a hindrance as, even if the opponent was not near the ball, my being inches from it is an obvious distraction and hindrance such that he could not approach the ball freely to strike it with my head next to it(which, even if he was still on the baseline, he could do, as the ball was not yet fallen). So clearly the person who hit the ball could not be allowed to blow on it. Would you then say that the receiver could do it but the hitter couldn't.
"Where's the REST of me?"
Ronald Reagan, in "Kings Row"