If you're timing is that precise and you can hit the ball cleanly that way it probably just reduces fatigue on the arm and allows more opportunity for using force through linear and angular momentum depending on the motions involved. In that event, it's as if your hand is just along for the ride once you set the racket in motion and you can direct it as needed. I think the service lends itself to that better than even ground-strokes though I wouldn't necessarily teach it to a student.
Here is an interesting take as applies to sports/ice-skating but considering loop and ellipse motions involved in most strokes and especially serving it probably helps explain why well-timed players can let the racket do its thing at some point rather than forcing it with muscle.
Angular Momentum for Dummies
I'm not suggesting that you try and calculate it but rather know that it exists. It probably explains why players using the physics of rotating bodies, ellipses, loops, and the gains of falling objects can harness these forces naturally and seemingly hit with little effort. It allows them to loosen their grip.
Timing is everything
