i think there maybe some crossed wires, the GP smooth-scroll is designed for single page sites where the links jump to a section of the page. Smooth-scroll just scrolls you to that position instead of jumping there. It won’t affect the way the mouse scroll movement works.
Looking at the link you provided, i am not really noticing the effect you are looking for. It seems more like there is a little bit of resistance when scrolling which i think is an undesired effect from the scripts being loaded on the page.