yes, the rail and your skis are not a smooth surface , the friction grips the skis on the rail. With more weight there is more friction and more grip.
However it is harder to do switchups, spins, ollies, etc.
I tried my friends PE's that were like double the weight and stiffness of my Troubled Youths and they were rock solid on rails, but I would never get skis that heavy because it would be impossible to get on the rails, and harder to do switchups and spins, etc.