Strut tower braces have a dual function [Actually 3, if you count coolness and looks!].
For the umpteen jillion normal bumps a car sees, the tops of the strut towers will migrate IN, and a bar will prevent long term sagging and changes.
For high speed turns, the tops of the towers go OUT, and the brace helps stabilize things.
BTW, don't preload the bar. Set it neutral.