Waldner's forehand position

Master Rosario ,

Very often pro players plays forehand-topspin with right shoulder(for right hand players)  is more down from the other.

Example :https://youtu.be/Qc-1oszmjFI?t=41s

Why?

Hi Il,

Waldner has dropped his shoulder at the start because he is caught slightly out of position and needs to get the bat lower to lift the serve.