[mhb]

I don't know either, but is it possible they are concluding that the bugs have only the function "move in a random direction" based on their observations?

If the bugs had the functions 1) move in one direction and 2) turn, then they might have observed a circular or spiral path.

[jameshart]

Put a blindfolded human in a zorb on an uneven patch of desert and I would be impressed if they could manage more than one bounce in the same direction in a row. Not sure what mechanism would enable a jumping bean to reliably bounce ‘forwards’.