One issue I can think of with putting that specific video on the steam page is that it isn't Arcen's content. It's polaris's and they get as revenue from it etc. I agree it is an awesome promotional vid for the game, and would be great to get it out. But officially posting it on he steam page would probably be a huge can of worms for Arcen.
That all said, I'm saying that without any actual inside knowledge or anything. Just guesswork! And maybe they could sticky a link to it on the top of the steam forums?
FYI, I'll post when I see part two and edit the original post to include it.