Ehh, that would make them mutants and persecuted against. I'm sort of doing it where they just were other evolved species that humans knew before the war, basically so I don't have to make everything super awkward, mutated characters are just FEV experiments from the ground up and join mutant friendly factions. You have to basically "choose" that sort of pathway in your character, they're either FEV mutants or they're pure and allowed in the more human minded factions.
Yeah, basically it's to prevent lore conflicts. Sort of like how in the Sonic fandom Mobians are accepted under the G.U.N, so instead of making furries a FEW mutation and really messing up the lore, furries are like a pre-approved race that can be mutated by FEV, if you want your character to play as a mutant with the option.