A large display increases the angular "cone" in which you can present the gun and still have dot in the window. I think the lower the display is to your hands, the "angular cone" in which you "get the dot" is much closer to the fulcrum point of your hands, and, the lower the optic is to the slide, the more simply lining up the slide in your peripheral vision will create success in "getting the dot". I'm not even talking about new dot shooters fishing for the dot, but rather, peripheral clues in a subconsciously visually guided index for experienced shooters, like came up with Craig in a different dot thread.
In a perfect world, in every single presentation, whether one handed, two handed, odd position, rainy, cold, weird dream last night, heavy turkey dinner, etc, our index would be so perfect that even with a tiny window mounted high over the gun, the dot would be directly on our point of aim, but that's not the case in the real world and small things add up.