One of several advantages of the high drive design is that it keeps the slack from being stuffed under the rollers.  A high drive always has a place for slack between the sprocket and the ground, whether operating forward or reverse.  

I'm not so sure just how much this applies to a tensioned rubber belt.  I realize the machine you showed (what is that, by the way) is a CIH style positive drive but it is still operated under considerable tension, unlike steel track or the steel-track replacement which runs on conventional steel-track rollerframes.