Well that is debatable. I just watched the segment and just before he brought up the gtx1070 he said about 5 times that the gtx1080 was twice the performance of a Titan X so if you ask me he was reffering to VR in this segment. He could easily cover himself saying it's faster than a Titan X because he never mentioned if it was VR or not.
It was in reference to using a 1080 and their simultaneous multiprojection. This is basically a VR technology, though there was some article about how it could help 4k gaming. Essentially, you are rendering multiple views, with the outside percentage of the image in a lower resolution. Really, they'd been working on this for a while and previously called it multiresolution shading. Not actually new.
So, this is useful for VR because you have a really big FoV. And it's not normal for people to use their eyes to look around to the edges of your periphery. Typically, if you want to look at something there, you move your head most of the way and then maybe move your eyes a little bit. In other words, you can get away with a lower resolution on the outside edges because it wont be seen quite as much.
This is less useful for 2D(like with a 4k monitor...) because you will be looking at the edges of the monitor a LOT more than you will in VR since it takes up a much smaller percent of your FoV. I dont know why anybody would want to have a 4k monitor and then render the outsides of the image in low quality. It would look bad, though obviously it'd help performance. I think preferably, you'd simply lower the overall resolution if you really needed the fps that bad.
And in terms of the '2x' figure he was saying, basically it was in comparison to a Titan X NOT using the tech. So a 1080 *using* simultaneous multiprojection is 2x as fast as a Titan X *not using* it.
The reason I'd call this misleading is because from what I understand, a Titan X could use it too and it's not a technology that would be limited to GP104 unless they're using some sort of new hardware feature here that I haven't heard about. So I think this is just a case of putting into context how when *combined*, the new card plus the tech can produce huge gains for VR(or on a monitor if you really wanted to, but I dont think you would).