Over rotating the mast will deform the wing shape you are trying to achieve. This could severly affect the point where the airflow separates from the airfoil drastically reducing lift, i.e. power. Maybe in lighter air it was a help.

I know on my TheMightyHobie18 with the mast rotation adjustment, we never have the mast rotate past 45 degrees from the centerline. Often we limit it to less.