It's more difficult to develop for, so could take a lot longer, which costs money, which means the whole project could be canceled. At least leading on the 360, they know they can get that and the PC version done if worse comes to worse.
Well I suppose that makes a bit of sense logistically if you feel your project could be shuttered mid term, and given the times who knows?
I just want to use this post to also note that I came to the realization that in my initial post I never pointed out what led me to believe the footage was from the 360 version of the game. At many points through the course of the footage the character would go to take an action and a big green (A) button would appear, or so it looks like to me. It looks like a system used in many games where they require an action button. Now there is no A button on the PS3 controller that I can recall, and while there is an A on the keyboard they aren't typically green. This is what I am trying to show people in my above image so I can gather some more response.