I recently saw a coach teaching students to lean forward on the transition volley split step, so if someone touched their back, they'd almost fall flat on their face. The reasoning was to hit out in front and cut off angles.
This is ridiculous.
What about a ball hit to the left, right, or lobbed..? The entire point of the split step is to move in any direction, and that can only happen if you're balanced. With your weight falling forward, you're basically saying, "pass me."
That's the difference between Andy Roddick barreling into net and Roger Federer transitioning gracefully with pristine balance and posture.