He’s probably just blind in the very center of his vision and doesn’t realize it, because he sees the brightness around the blind spot, and the brain is pretty good at ‘filling in’ missing information.

I saw a video a while ago about a helicopter EMT pilot who got hit with a laser while flying, and he’s blind right in the center of his vision. He doesn’t notice it most days, but he’ll catch himself looking ‘around’ things he’s focusing on to actually see them.

Your colleague probably doesn’t look long enough that he feels the ache/burn of the UV rays, or if he does, he assumes it’s something mystical, like the eyes producing vitamin D.

Boy is he gonna be surprised when he no longer can see the sun.

Unless he was pulling your leg. That’s always an option.

Being outdoors during daylight does reduce myopia compared to being in indoor lighting.

This doesn't mean stare at the sun though. It means be in high brightness areas.

I believe that's one of those "doctors say it's bad for you, so it must actually be good for you" conspiracy theories. Kinda like antivax, but opposite "logic", I guess.

Edit: https://www.allaboutvision.com/eye-care/eye-health/sun-gazing/