Part of the fun is immersion. A player can easily suspend disbelief if it's important for the game's conceit (it's like our world, but with dragons and magic). But if it's based on a misunderstanding of the base nature of the world, it's just a distraction with no value.

Sometimes it can be fun to get into the medieval mindset and have the rules reinforce their erroneous beliefs (maybe bloodletting is treated as a useful treatment for diseases, for example). But in this case, if the armor types are based on a misunderstanding in the Victorian era, I don't really see the fun in pretending that these other types of armor both exist and would be useful.