I have 2 mountain biking full-face helmets and I cannot see the helmet while I wear it... meaning I lose no peripheral vision plain and simple.

Okay, I can see the visor (when in place) and the chinbar, but there is no impact on peripheral vision to the SIDE, which is where I would detect other road users.

It's a bit of a moot point, since I then put on a pair of snowboarding goggles that DO impact side vision. But that's not part of the helmet.

DOT Motorsports helmets and ASTM-F1952 cycling helmets are different animals, there isn't much point trying to extrapolate the performance of one from the other.