A few things about the video that make me think the unit is a knockoff/fake:
1) that plastic sheet s certainly not the protector Apple puts on their phones. I don't know about preproduction runs but at least that's not a protector any consumer would ever see.
2)He doesn't appear to click any buttons but the screen is on and it appears very "flat" an has a lot of color saturation. Compare that with the real 6+ he shows that appears washed out and the saturation changes with angle while the prototype phone shows no color shift with angle change. I COULD be the next iPhone screen is really that good, but it looked more like a printout than an LCD screen to me.
3) The home screen appears static. Even with Mr. Blurrycam I think we'd see the parallax effect at least a little on the video.
Not saying it isn't a real next iPhone but it seems "off" in some very suspicious ways. It wouldn't take much work with a 3d printer and some paint/decals to make such a thing in a few days. Add in in the suspiciously low-res and it just doesn't add up for me.