I never understood the point of this. How does this create natural timing? Hitting it off one bounce encourages you to move your butt, hitting off two bounces to me seems like it would just result in sloppiness. Moreover, the biggest difference between the wall and an opponent is that the ball coming off the wall is going to reach you sooner (less distance covered), but will be travelling slower than a ball from an opponent. The biggest timing issue from me when going from court to wall to court has been the stroke timing with regards to the pace on the ball itself.