If they have a very distinct culture and way of life, it would make it more difficult for them to assimilate into the existing Elfrieden society. If the other human tribes, that possibly arrived as refugees, were more similar to the prevalent culture in Elfrieden, they might have already left the refugee camp life behind and become a part of Elfrieden.Maybe it's just me, but I kinda feel weird about seeing all the (shown) human refugees drawn as Native Americans
In all likelihood, as mentioned in the story, they're just the representatives; it's just odd that we haven't really seen any other human refugees yet
Inb4 MC proposes the concept of native reserves (doubtful since he'd still need to tax them - unless he settles them in unclaimed land)