Actually, it is. Technically whatever is left of F. Irvine is in Irvine now. He is the new Fused Irvine. Same powers. And they look basically identical. Remember Kioet saw both Irvines AND the after-result (all at different ages). Only difference now? Hair color. I don't mind telling you that my hair color changes every month or two. Plus Kioet is a Trandoshan. He likely isn't using hair as a physical identifier anyway. It's just so much more clothing accessories.
By the way, they're still all named the same name, since besides the fact that "Cracern" was never been used in PtH by anyone except Irvine Cracern himself, he no longer has the memories of choosing that name.
'Tis what you get for using the same character so many times.