Your eye is still open under that flap though, no? I dabbled in Olympic pistol shooting back when I was doing across-the-course service rifle, and I was told to always keep both eyes open by the dude teaching me. Same for service rifle (and later palma). I always found that closing one of your eyes fucks up your focusing. If you don't have the little flappy dealy, you just do your best to defocus/deprioritize the view out of your non-dominant eye. I actually went for quite a while without any sort of cover because it helped me avoid cross firing (which is probably more of an issue with across-the-course than with Olympic pistol).
You're absolutely right about the lack of spectacles though. This guy is one hell of a marksman.