The original paint was gloss. A fan gets beat by all the bugs and dirt coming through the radiator and goes dull pretty early in life.
If you find a clean car that’s not all rusted up and remove the fan to look at the mounting area the gloss paint can be seen.
Just like wheels, everyone says Satin. Well get a clean one and remove the tire, and look at the finish, it’s gloss under there where it’s protected.