I don't know for sure about the stage but I'm pretty sure it is only for really big meets (Iowa and Oklahoma State). The other two meets I've gone to it's been set up like volleyball with the curtain.
I've never seen us use the stage against anyone other than Iowa. The first time I remember seeing it was 2009 but it could have been used before that. The NCAA championships use a stage for the championship matches so I think it really gives the meet a big time feel.