What I've come to realize by reading this thread is how ignorant so many people are not only as to how the human eye works, but also the physics of lenses in general aka optics.
Anyone who mentions that the magnification feature has anything to do with human eyes focusing is flat out wrong. The only one who seems to know what they're talking about is the OP and those he convinced. Even then you can tell from some of their responses and defenses of him prove that they really didn't understand the concept he was attempting to prove lol.
No matter how you choose to look at it, the way human vision is portrayed in the game is going to be inaccurate, for the reasons the OP stated. But the developers of the game have come up with an interesting way to restore how accurately we would actually view the scale of an object by giving us the shift-zoom. Instead of looking at the feature in game (the SHIFT zoom/magnification) as a temporary enhancement/cheat or whatever, look at it as if the rest of the time when you aren't using that feature you're actually "zoomed" out less than you should have been all along and by using shift, you're actually putting things in the natural perspective you should have had all along (in terms of judging scale). Now of course by doing this, you're even destroying more of your peripheral vision and making the original problem of not being able to fit a human's entire field of vision within the screen, but when you're aiming down the sights, the developers know that your peripheral vision matters even less at that point because you're eyes are focusing on shooting something, so it's okay.
In other words, what most people are doing is viewing the default view when you run around as the way things really are so when they see objects magnified using shift, they think it's a cheat. They don't realize that the default view is actually hindering you from seeing things at a scale you should be viewing things at all along (they're all much smaller than they should be), so the shift feature is simply fixing how you should be viewing things all along (correcting the scale of objects seen). Basically, everything in a scene was SHRUNK down to fit on your monitor, the "zoom" feature corrects that by temporarily UNSHRINKING the image when it matters most and when peripheral vision matters least, when you're aiming down the sights to fire.
Anyway, great job LHeureux and thank you for coming up with an excellent visual way of depicting what the SHIFT feature is really all about.