The purpose of the pvp test is to make sure pvp mechanics are working as intended, not to hype the server. They want players to look out for bugs and report them on the forums. I believe this is why they only want players who are subscribed and reads the forum. I think an open beta works best when players have access to all content and not just pvp.
But they already had a Beta-stage - this will simply be to test their BG fixes - mainly AV and AB.
