@Centurion:
That used to be the case. “Backroom” is still a special Member Group (just like Europa Barbarorum is) which gives you access to associated forums. Which in turn means only “Europa Barbarorum” members should be able to visit EBH and only “Backroom” members the Backroom.

However at some point the forum staff decided they'd like more souls in the Backroom and extended membership to automatically include every member. Backroom is still invisible for people not logged on as a member though.