Technically you are correct and incorrect every walking anim replacer is a levitation anim replacer
Just because the walk animation is used while levitating, that doesn't mean that a walking animation replacer also replaces the levitation animation, as there is not a levitation animation to be replaced. Levitation just allows vertical movement using the walking animation.
Maybe some other animation could be hijacked and forced to play if you are levitating. I recall something like this wanting to be done to swim in water meshes places above water level, but I don't know if it can be done.