I don't understand why they're trying to pass off 8472 as 'mysterious shapeshifters' and 'a previously unknown race.' They're 84-frickin'-72. They showed a picture in the video, for crying out loud.
to get those who are new to star trek or haven't seen voyager interested in the game. don't forget they haven't appear in any other TV shows or for that matter any other medium ((if they star trek wiki is to be believe)). so they would be a good attention grabber.