Personally I think there are two possible reasons they're not charging for it.
1) because they know that if they did there would be trouble because they know they can't devote enough man-hours to the project to deliver something worthy of charging for... (Think about it. NO listed company would release something for free if it was worth paying for).
The problem is that from a PR perspective, it's pretty hard to ask money for a what is basically a rework of content that's already there, regardless of what the update is actually worth. In other words, the reason it's free is probably not because it's not worth money, but really because trying to sell it would be a mistake. Many players would feel like they're paying additional money for something that should've been there since the beginning.
To me this "beyond" pretty much feels like frontier simply wants to fix what needs to be fixed and add more polish to the game before selling more expansions.