OpenMW doesn't report all the potential resting hindrances
If Morrowind.exe knows there are enemies nearby (Morrowind's detection is not always accurate on that because of how it works in general...etc), and you're levitating or water walking (for example) and try to rest; two notifications will show up, one about the nearby enemies and one about the player not trying to rest on solid ground, OpenMW would only show the one about the enemies nearby.