This is awesome. I wonder how it would feel if just the selections scrolled, like Apple’s interface for setting alarms and timers.

I especially love it because it leaves open the possibility of interacting with the rest of the screen while an element is picked. Eg you could navigate a directory tree while finding the right place to put a file. Though I guess it’s similar to cut/paste in that respect.

Yes I think on mobile, having only the list scroll would be great. I actually had the Apple alarm interface in mind for a bit but thought implementing it would be more difficult. But you're right, it's probably a better experience.