I think this can´t be intentional.
The player can jump on lower floor walls by using the feather from the top part of the wall or the top sides of the stairs and slide.
this allows the player to bypass alot of stuff in dungeons and has a big risk of getting stuck in dungeon parts/objects
and inescapeable situations.
This problem severly limits the way you can build dungeons with the feather and lower floor parts at the same time.
A similar problem exists with the jumping enemies such as skelletons jumping down the walls and getting stuck in objects and lower floors
that you and the enemies shouldn´t be able to jump down because of objects blocking on the lower floor.