So? This is the way all these showings are done.
It wasn't shown on the Xbone, and many of the 3rd party games has exclusive content for the PS4. They will be best on the PS4, and look better than anything that was shown on the Xbone
Not really. Games are often demoed on PCs built to the console specs.
Yep. Usually they use the components from a near-final console build put together in a PC case.
The controversy is there were at least 2 XB1 booths where their demos crashed to a Win7 desktop (the XB1 is based on Win8) and when they opened the cabinet at one of them to reset the system, someone caught a photo of a high end PC, including a GeForce GTX GPU from nVidia. Like the PS4, the XB1 is built around an AMD APU (integrated GPU on the same chip as the CPU).