I don't know, I'm not an expert but the strop on the picture is so short, like 6 inch and mounted on a hard surface. I've seen both Kochansky and Ray Mears using their everyday leather belt either tied to a branch or hold by a foot and they hold the other end with one hand while the other will do the rubbing action. They take advantage of the entire lenght of the belt by rubbing the blade, dragging it lightly back and forth to the point that it may come hot from the friction.

Either on the inside or the ouside of the belt, I guess it doesn't really matter.

It's supposed to remove the blurr and reconfigurate the edge to a convex shape, like a microscopic gothic window from a cross section point of view.

Ray Mears even finishes with a few strokes on the edge of a vehicle window if it's available to give the edge a little more bite as he says...

BTW check out this instructional youtube video for stropping straight razors but it's probably pretty much the same principle for a bush knife.

Frankie