Okay I'll bite
From a design standpoint, doors exist to impede player progress and block sightlines. An always-open door is purely cosmetic and therefore doesn't need states to begin with. Therefore it can be assumed that to have relevance, a door's default, or "0" (off) state must be closed.
So if we presume it HAS to be one or the other, when a door is open, is it on or off? Discuss.