Wrong you just don't understand what you seen. nowhere in the documents did you see 6-8X the Xbox 360 for games it only said that the performance target (X360) ~8X that's the full system but only 6X the power of the Xbox 360 will be used for games because of the media stuff & Kinect.
from the documents
"
Key Talking Points:
Next Gen Gaming/Kinect
720 and Kinect v2 will afford creators and publishers the ability to design and build the next generation of core experiences.
Specifics:
Game developers can tap into full CPU power of the platform, leveraging 6x improvement in graphics, dedicated application processing and systems pools, complete separation in NUI and game engine resources
Kinect Device will have better FoV, better depth, better voice support and higher tolerance for variable lighting scenarios
A new and more accurate Kinect sensor and fully dedicated application and system resources will enable the delivery of a whole new generation of Kinect enabled experiences. "