Originally Posted by dlam
title speaks for itself.
want some opinions about whether or not this biomechanically sound.
Sure it is sound, but it isn't something to focus on in isolation.
The more athletically you play, the greater the odds that both feet will come off the ground. If the opponent hits more topspin, then it is also more practical as jumping can lower the contact point.
The pros come off the ground more than a lower level player, but they are usually swinging harder and hitting against more topspin. But even they are not going into the air on every shot.