I don't usually get into lore discussions like this, but I thought maybe someone here would know more than me or we could come up with theories together!
So, right, the pokedex entries for SWSH say that, specifically Sizzlipedes and Skorupis share a genetic ancestor. Specifically, it says
This raised a lot of questions in my currently insomnia addled mind. A lotta bugs are segmented, like sizzlis and skoops, this would most closely match the isopod-y Armaldo. Tons of bug types have mustaches too, some super similar to one another (Golisopod, Orbeetle and Drapion sharing one style, Centiskortch and Kricketune, etc). Do y'all think that means there's basically two primary bug ancestry groups? Isopods and not isopods?
If anyone knows more or has more ideas I'd love to know.