I believe it's because they aren't actually part of the faction. I think it generates a different type of pawn then re-dresses to match the role requirements. Given the way this mod works you're unlikely to be able to work around that at this time.

That's a pity, thanks anyways for taking the time to answer

No worries. I do already have one way to knobble similar oddities in the form of creep joiners by making a fake faction. This is sort of a different problem but I’ll have a think and see if I can make it work sensibly at some point but it won’t be a simple task given how different it is to the rest of the mod

That would be amazing. Maybe reach for others who implemented faction generation into their framework (like the Vanilla Expanded crew)? I don't know if it's relevant, and maybe you already thought about that.

By the way, is there a way to set which raids that faction is allowed to do, using this mod? What I'm asking is if it's a feature I've missed or if it's not in the scope of the mod

Definitely out of scope I’m afraid. Many raid types are hard coded. I can potentially work around them one by one but that’s a never ending eternal black hole of manual hackery