Hi. For some reason I keep occasionally getting vanilla enemies with this mod https://imgur.com/a/H2nqFa3 . They seem to be neutral and only attack when you do. I most often notice them during what I think is biter migration, but very rarely during normal attacks as well. So far it was nothing but medium spitter, but shouldn't vanilla enemies be totally replaced by this mod?
The only mods I have that may impact biter distribution/evolution are Edit Map Settings, Krastorio 2, Rampant fixed and Alien Biomes.

Yes, Vanilla enemies will occasionally be encountered. This is due to the fact that the squad of settlers is replaced by standard spitters at the moment of giving the order to create a base. Since due to a bug in the factorio some attempts are unsuccessful, these "settlers" then go on the attack.

It is also impossible not to replace the settlers, since in version 2.0 the order to "create a base" for non-standard biters leads to the disbandment of the squad instead of the appearance of nests. This is true for early 2.0 versions, I don't know if it is true for the current version