Uhhh.. more that you don't understand its multiplayer support, which works fine.

The default levels for each of the game modes you can host are a series of levels compatible with that game mode. To change it, select the filename, and type in a new filename (one that is compatible with that gametype). It will play that one until someone (or a team) wins, and then will go to that level's next level setting. If you want to change gametypes, either get Project Controller or restart the computer, though.