Almost every program and app used today has tabs. Someone not knowing tabs today would have to be a novice at computing, using a cell phone, a kiosk, many games. Almost like they did not exist one day then did the next.
This Scenario has been planned for some time and lots of information has been posted about it. Folks have been able to load the terrain for awhile in the assigned arena. Just all of the sudden not knowing anything about it is odd.
That being said, I really do not see an advantage to using tabs in the arena selection. I am not privy to any planned future expansion, but at least for now, why do we need them...