No, maybe, I don’t know, if there is it’s unspoken and unenforced because I’ve been doing it for years and no one ever complained to me.
Some people think they’re saving a bunch of time by using a urinal over a toilet but honestly it’s 5-6 seconds at most if you use it the same as you would a urinal, no sitting down, no pulling your pants all the way down, etc.
Do you think that you need to pull your pants all the way down and sit to use a toilet to pee, if not what are you doing in the stall that wastes a ton more time? It’s not much slower from my experience just do it the way you would a urinal, with the only difference being that you have a door and real walls.