I've wondered the same thing, Periodot. And I also use other vBulletin sites on my android phone and see the full site. I dislike the mobile version, but I assumed it was because this site was so huge.

I don't see a version number at the bottom of this site or the other one I use, but it has the same footer/copyright, which is:

Powered by vBulletin® — Copyright © 2000 - 2011, Jelsoft Enterprises Ltd.

Maybe I'm not looking at the right place?