I know what it is. The only thing the non-modded game can do is set aside the number of public and private slots. In this case say 22 for public, where anyone can use it. The other 10/11 would be considered 'private' and you need a pwd to join to use one of those slots. However you can never go above 22 public. So unless you use a pwd you cannot join as player 23. Or, if all slots are taken... 22 public players and 10/11 private... nobody can join even with a password and boot a public player. This will happen before any downloads. Now, this will not preclude someone using some external method outside of the game to boot someone before joining. Typically only senior admins with rcon access can.