Jesus Christ it IS disabled by default. I just now downloaded the installer, installed it to a new directory and ran the tutorial with no problems. I also re-installed v11, had it auto-update to v12 and had no problems. I honestly have no idea what you dumbasses are doing to encounter this problem unless you are actually enabling the add-on manually.
The only way you could possibly have this add-on enabled automatically is if you installed the game and ran a dedicated server before ever running the normal game.