Point taken--
But I still contend that rolling a boulder-like object down a hill is much different than a 'creature' rolling down a hill.
If we really wanted to make this complicated, I would like to think you should be able to move further than one space when going down hill... as the object converts the potential energy of a high place into kinetic acceleration. So if you started at a '4' mountain, rolled down to a 3 mountain, then to a 2 hill, and then onto a 1 plain, I think you should be able to do this all in one movement.
IMHO anyways.