I still encounter people using the bathrooms being under construction although the toilets and other items have not been built yet and the room has not been opened yet. Working as intended?
You know the saying: “When nature calls…”
But on a serious note, I suppose that’s a bug. I can’t imagine it being on purpose.
Well…they seem to defecate on the blueprints in a dark room and even pay for it. While this is funny if you are not a janitor… 
Funny issue lol!
Report the bug for devs take a look on this issue ;
This is in game since the very first day… bug reported it long ago ;).