User blog comment:Kogath/Monster Hunter XX Discussion/@comment-26116038-20161101124417/@comment-26261665-20161102011758

They are considered subspecies in-game. Them being later stages of its life doesn't change anything because in the end they are considered subspecies. Going by the lore Oroshi Kirin and Ashen Lao are not subspecies, Black Diablos is just a female Diablos on heat and Shah Dalamadur as well is not a true subspecies, yet in the game they are considered one. While Crimson and White are in fact just called Fatalis on the game, them being later stages of its life is not a valid reason to think they would add them. Not to speak that White is not related to Crimsom and normal Fatalis as stated in the lore, it's not an older Fatalis like you suggest.