The Kermode bear Ursus americanus kermodei is only found in British Columbia,Canada. The Kermode bear has single nucleotide polymorphism at the melanocortin 1 receptor gene (mc1r) locus which cause the white color. 1 out of 10 indviduals are white and are refer as Kermode bear. However, is the black version of the Kermode bear still a Kermode bear Ursus americanus kermodei? If not, why?
It is because somebody wrote a paper that described it as such, and the paper was published. I don't mean to be flip. Its just that taxonomy is done through publication, not committees (although the peer reviewers could be considered a kind of committee). Subspecies are less stringently regulated than species, and this subspecies does have a particular unique set of gene frequencies that occasionally (as you mentioned) show up in the phenotype. The fact that it has been culturally recognized as special may also have something to do with its subspecies status. A subspecies need not be reproductively isolated from its parent species, and need not have any fixed characters.