Look at the distance from the dock icons to the "page dots" on an iPhone there is very little room between them, on an iPad, like in the picture, there is much more room.
Maybe, in the new iOS 5.1 they removed the reflections. Or maybe its just a really good photoshop, but if you look at the full resolution image, it really doesn't look like a photoshop.
One way I could imagine faking this, is if someone took a picture of an iPad home screen, then photoshopped it to be higher resolution, and put it on an iPhone 4/4s to emulate the retina display. But I feel like if someone was going to go through all that they wouldn't of photoshopped out the reflections. Plus you can see what looks like the iPad bezel below it, and not the iPhone bezel which would have either the speaker or the home button visible.