Well... I would imagine that the original OS they were planning for the X1 might have used somewhere in the 1-2gb of Ram while sitting ready to snap functions into play at a word to Kinect, but what more than likely happened was after the E3 PR explosion they had to start modifying the OS to change the drm situation and to tack on more and more bits to make sure it all worked smoothly for launch day.

I'm sure once the first big update to the OS comes in it will have a more streamlined version of the OS where it wont need to be multiple builds all glued together but one that they'll have had more months to alpha/beta test properly and ensure it has a smaller footprint, should mean games later in the X1's life should have a far greater about of the Ram for themselves to use. Hopefully.

The dick in the box type obviously.