Can be done on an MUP with care, it does go wide when starting and accelerating, but it's not as wide a path once you get going. I do agree passing is difficult, but I can't see me ever passing anyone except a ped.
One big benefit of a bike is you are not using calories to hold yourself up, you are sitting. This thing is a lot more work. Walking seems more efficient. ??
I only rode it mostly on a flat with very slight incline and declines. I'd rather pedal the the trike with the dog in it up hill, all 120 lbs. It seems like less work?