This might be a minor logical glitch but never-the-less it is up to you to decide this.
I had my status set to hidden when I joined an alternate shot game.
After a few seconds I could see we was 4 players waiting in the lobby for game owner to kick off but he/she never did this.
Another player asked in the message box why the game wasn't started and owner replied with "we are only three players". Obviously my presence wasn't shown but I anyway held a place in the game "prohibiting" them from launching it.
Either I should become visible for other players in the specific game I join or I should not be able to join such a game at all
(a third option might be to get a warning message to take some action)