Did the ball stop moving? Were his hands moving? Was the ball stationary relative to the hands? Was it stationary to one hand and not the other? How about part of one hand? - those 3 fingers it wasnt moving even thogh rest of hand was bobbling. Any ball the bounces back towards the QB must theoretically stop going away from the qb and change direction. By your definition that is a reception and a fumble. Later in your post you mention "control". Would "grip" therefore become a part of your definition? How do you define that? The naked eye, a ball can bounce off a players hand and look like a drop. If you slow the video down, there is probably a moment, a micosecond, where the ball is in contact with his hands and it is not moving. Then you will need to add a time definition to your rule. Then it starts sounding boring and slow process to determine catches.
I think you would have more issues and problems with this definition.