The colimated gunsights work just like the modern red dots on rifles.
The sight projects a crosshair in front of the sight and the shooter can scan aim and shoot with both eyes open. You don't have to close one eye or move your head to the side to aim. You look with with both eyes at the target, one eye through the sight, and the brain will automatically create the combined image, with the dot in the midle.
Shooting both eyes open, specially with reflex sights, has some clear advantages, specially in a fluid combat situation, where your periferial vision is very important.
Same in a 109. The pilot didn't zoom in, or moved so much like in the game. The sight was right in front of his eye.
So Lixma is in a way correct. We have two eyes and a brain to combine the two images.
This looks quite good.
Of course our brain is very good at bluring things close to the eye that we don't focus on.
I kind of agree. The Shift+1 image is unnecesary restrictive in CoD.