I don't understand this at all, I really think you might be misunderstanding.
a boy goes in with the mom to the ladies room. there are stalls no problem most ladies don't mind if he averts his eyes and is well mannered. My son is 10 and would have no problem doing this if I felt the need in a highly crowded unsafe area.
Regular places that we are familiar with and are safe, low crowd, decent people, I give him the rules, and send him in and yes I wait for him Outside the door.
So if this is the scenario and you are saying the mom pacing outside the mens room is requesting men not go in until ds is done, then yes the mom could politely request that, Honestly it seems unlikely to me that there would be a man on his way in, mens rooms are never busy. Since men are not nearly as understanding, I could see them getting impatient, but how long is it taking kid to do what he needs to do? serious 15 secs to whip it out, pee and tuck it in. carry some handsanitizer and use that.
It might depend on the place high traffic no this isnt' going to happen, but a small restaurant maybe. also the number of stalls might influence it.
I dont' know weird question. Either they are old enough to go alone or they come with me, that's how I see it.