Not sure if this is a bug or by design.
But you can create a game in non-ladder mode and then go back and switch it later to ladder mode. I discovered this when setting up a 4v4 game and I accidentally left the ladder option off. The other team wanted a ladder game so I went in and just changed the setting and saved it and it worked.
Made me think this could be a way to lure players into ladder games by posting a game as a non-ladder game and waiting for someone to join. Then coming in and switching it to ladder and starting the game.
KGB