R. Star wrote:
Why can't they be different subraces of the Xindi insectoids?
With a different number of limbs
? You might as well ask why spiders can't be a subspecies of ants. The differences are pretty darn enormous. Frankly it's rather mammal-centric to assume that two species have to be related when the only thing they have in common is looking like arthropods. Imagine a Kaferian looking at humans and asking why we couldn't be a subspecies of Caitians.
By your own admission, it's a stretch. It's unlikely they're related, and the burden of proof is on the unlikely interpretation, not the likely one. I don't have to justify the assumption that they're not, because that's the more probable interpretation on the face of it.