2-speed crankset for folding bikes works without a derailleur

I was wondering how that would work but it actually sounds really cool. My only concern for me specifically would be that I back pedal to horizontal position get ground clearance when going over things that the pedals could catch on.

The shifting mechanism looks similar to the Buffalo Utility S2 from World Bicycle Relief. But the Buffalo uses two chains for the two speeds. Contavelo say they use a gearbox inside the crankset. I’d enjoy a more detailed explanation - the best I found were these graphics:

Exploded view:

Low gear:

High gear?: