They DID Get xp if it was a deathmatch.
Devil just joined, and other peoples xp starts adding up from the moment you join, so when you enter a room everyones xp is always starting at 0.
Also, JstaNub did create it as a training room.
He either changed the gamemode sometime later or another gamemaster did.
Don't know how a gamemaster can change the gamemode of a game in progress though.