If I'm reading right, the two groups can only breed with each other. That is, white-striped males and tan-striped females can breed, as can white-striped females and tan-striped males. (And the offspring are about half white-striped and half tan-striped.)
So it's not speciation, any more than sexes themselves are speciation.
> white-striped males and tan-striped females can breed, as can white-striped females and tan-striped males
This alone doesn't contradict the two-species theory. It could be that white-M + tan-F is species #1, and white-F + tan-M is species #2. Sure, it sounds weird, but not nearly as weird as the idea of 4 sexes, IMO.
> (And the offspring are about half white-striped and half tan-striped.)
Now, this is the important part. As I understand it, the offspring of "species #1" could be "species #2" or the other way round. This indicates that #1 and #2 are the same species after all.
So it's not speciation, any more than sexes themselves are speciation.