Doesn't kinect also need gpu power?
Yes, but not 10-5% of the GPU resources only for computing the depth image. Even that 10% of GPU reservation on XB1 wasn't entirely for Kinect (motion tracking):
Digital Foundry: Microsoft returning the Kinect GPU reservation in the June XDK made a lot of headlines - I understand you moved from a 900p to a 912p rendering resolution, which sounds fairly modest. Just how important was that update? Has its significance been over-played?
Oles Shishkovstov: Well, the issue is slightly more complicated - it is not like 'here, take that ten per cent of performance we've stolen before', actually it is variable, like sometimes you can use 1.5 per cent more, and sometimes seven per cent and so on. We could possibly have aimed for a higher res, but we went for a 100 per cent stable, vsync-locked frame-rate this time That is not to say we could not have done more with more time, and per my earlier answer, the XDK and system software continues to improve every month.
http://www.eurogamer.net/articles/d...its-really-like-to-make-a-multi-platform-game