Hi. Only tried my game (endless runner) and FoxyLand so far and could not see any improvements. Dont know if FoxyLand update causes the heavy stuttering or if its a Xbox One X problem but it runs very poorly now (was fine on my old Xbox). But it may be an issue with the last update.
My endless runner (The very long walk) is still the same with some hickups and slowdowns. I hope this can be improved in the future for UWP games.
PS: I got my highscores back but sometimes it just returns 0 (but leaderboard shows my correct value). :/