Microsoft worked for years to implement this sort of file system in Longhorn, called WinFS. In the end they could not get adequate performance and had to strip it out.
Just to make it clear, the linked blog post is wrong; there is no data loss in this situation. All that happens is one more save point, which does not harm earlier save points. (aka versions)
My understanding is that Metro tends to sandbox an apps data in a way analogous to that of a mobile OS. I believe the intent is to prevent one Metro app from overwriting another apps data or corrupting the file system.
If Microsoft did this they'd be eviscerated crucified.
iOS Developer and Mac user here (as well as Windows).
The madness must stop. I have a feeling Steve will be missed more and more as the years pass.