Look, I get some people claim such amazing eyesight as to be able to instantly distinguish native vs. upscaled when you're in a room watching and enjoying a game demo, despite the fact that it requires normal people access to a direct feed screenshot with very particular sections zoomed up 8x to pixel count, while also making sure you're accounting for other intentional environmental effects that may blur or otherwise impact the image.
http://www.neogaf.com/forum/showthread.php?t=680289&highlight=pixel+counting
But hey, if you're saying you can tell the difference with enough accuracy to make a public disclosure about it, just by watching someone play the game, then I say wow.
I've seen a bunch of other 3rd party games running at various times, and I can't tell you the *native* resolutions of those either.
So me, I'm not making that claim. I'm sorry if you think that's a job requirement.