L200a vs L200b taxonomy

[kwf1800KWF]

I have had both. And other than the one having a higher dorsal fin, they are very close in looks.
I get that they can be two separate species. But how can they be from two different genuses?
I have read that blue phantom and green phantom are possiblity the same species or a subspecies of one another, that occur in different areas. So blue and green phantom can be the same (sub)species.
But the high fin green phantom is a totally different genus than the standard L200?
I am just confused about this. I would greatly appreciate anyone that can give me any information.

[Jools]

They belong to two different genera because they have characteristics that place them in different genera - bear in mind these can be features you can see (like the dorsal fin being joined to the back) or others you can't (like the length of the intestine). There is more in the species profiles.

Jools