This was on the front page:

ya weird. Crytek devs on Beyond3d stated that that game(Ryse) was on actual Xbox One hardware. So there is one.

http://www.neogaf.com/forum/showpost.php?p=63668486&postcount=24

But I didn't get in GAF... the image I get now becaus they have more into it but the first I got in Gametrailers.

And I know more than you

You can't bullshit a bullshiter. so don't even try.

Now that from GAF...

Jonathan_Blow: P.S. It is not true as the article says that "all E3 demos run on hi-end PCs". The Witness was running on PS4 dev hardware, and it looked to me like all the other PS4 games were running on dev kits as well.

artenvelope (sucker punch dev): @Jonathan_Blow Yup, we were definitely on a dev kit.

And just to give my opinion...

If the hardware is ready for the launch then everything is ok... they can use even a iPhone to show the demos in E3 since the hardware will be ready for the launch time.

My guess is that MS is still working out the heating issues. I mean they must have heating issues if they have a console larger than the original 360 AND a power brick. I just hope they weren't trying to pull some BS like "it was to show off the power of the One WITH the cloud." Which would mean that their games WILL NOT look as good at launch, something I don't think even the more hardcore Xbox fans would forgive.

Many software during presentation are not a finished product, there are still bugs that can cause crashes, memory leaks ... And of course publisher / developers want people to have a better idea of ​​what the product will look like in the end and to achieve this, they use more powerful build.
This is not anything new, many if not almost all publishers / developers have done this for several years. At least for unfinished soft.

that is so ridiculously funny.

So they're lying about what they've shown.

What else could they have said in their position? "We are running on hardware using a TITAN GPU"? lol.   They need to make look the XBO as good as possible.