So that means if I find screens from just the official site that has higher res than that, it is likely from PC? Whoa :mellow:
yes, although some have proposed that the mountain landscape image is a composite.
However, I think it was taken on PC, because the resolution is 3580x1000, which I can only guess was rendered on dual 1080p monitors and then cropped.
1920x1080 x 2 monitors = 3840x1080 (cropped to 3580x1000)
Since the vertical resolution is 1000p, it is impossible for it to have been rendered on Xbox (max 720p vertical resolution). Even if it were a composite of multiple Xbox screens, the vertical resolution would not be greater than 720p.