The NDA is still up for two reasons. The first reason is as people have mentioned is because of story. The second reason is because they haven't fully developed their absolute final release build. As of now, they can still cut stuff or add stuff. Nothing gets the internet more angry than finding out about a feature only to have it cut prior to launch. By keeping the NDA in place, they avoid their forums being flooded with, "WHAT THE HELL, BIOWARE!?!?! WHY DID YOU CUT <Insert feature here>?!?!? THAT WOULD HAVE BEEN AWESOME!!!!"