Most unicycles coast if you let them. I don’t think it would make it easier keeping your feet on the pedals in the weak position (with them up and down not horizontal) than putting them out of the way on top of the frame, except for on bigger wheels perhaps.
I find the easiest unicycles to coast tend to be 20" trials or freestyle with a flat crown and a relatively high seat. The 20" makes it easier to get a not too bent angle on your knees with your feet on the crown. 24" is fairly coastable too but 29" and bigger gets almost impossible to control with your feet so high up.
I always thought coasting on a unicycle was impossible (even though I had seen people do it) but just like any other unicycling skill it is possible and even not too hard with a bit of dedicated practise. If I can do it anyone can do it- cos I’m not that great at tricks. The beauty of coasting is it is less wear and tear on your shoes and tires than gliding once you get the hang of not falling off too much.
I spent a month learning how to ride the one in the video. It was definitely a challenge, which is also why I enjoyed it very much. The best run I got on it was maybe 50 yards, but had I remained determined and kept at it I’m sure I could have become somewhat proficient on it. I don’t see why so many unicyclists are put off by a challenge. If anyone can build or obtain such a unicycle, I’d recommend it highly.
My dad made a couple they’re really fun! It’s a bit like regular feet on frame coasting except you’re more… Stuck to the unicycle…
The first one he made had a back pedal break and is significantly easier to ride, you can control the speed down hills which means actually being able to go down hills!
I don’t think you could practically go from A to B on a normal freewheeling unicycle. I’m not saying unicycles are the most practical vehicles but I’d want to at least be able to stay on the entire time.
Although maybe for skateparks, stairsets and freestyle routines, but not distance - never distance.