wahoo,
I think the weight of the plane has everything to do with how much torque a servo needs. Post that link and enlighten us please.
Try telling that to some of the 3D fliers using massive control surfaces and throw rates.
I think its a combination of both. Even on heavier planes that have small control surfaces and reduced throw it does not take as much servo torque because you can use the mechanical advantage in the linkage to your advantage.
Ed M.