Underp4ntz it is a problem of older days, when optical coatings were expensive and problematic in maintenece;
it also requires very specific circumstances to occur, like user (spotter, sniper, range finding equipment) being positioned against the sun from observer's perspective, not camouflaged and actually exposed to direct sunlight; ofc weather and particles have impact on that as both rays and observation are obscured when light diffracts on the way, to various degree;
so if you ever get a game where a scope giving is off a glint in the middle of night with no light pointing at it, just throw that game out of the window ':D