Were people really thinking, "If I unplug Kinect my games will boost up in framerate!?" If so, wow. The responses to Nelsons tweet on twitter are kind of funny, like people just automatically assume the dumbest possible scenarios.
Why do you think that snapmode will not work on games which use these 10% ??
This is just the resources saved for Kinect => has nothing to do with snap mode.
It seems people just aren't looking at this from the right angle. To me it's something like, if the developers didn't take advantage of extra Kinect functionality (like the vast majority of games) they still couldn't have used the extra resources in the past, whereas BF4 took advantage of this to feature head-tracking, therefore utilizing the reserved power.
I'm under the assumption that the OS functionality is always there regardless.