This will forever be an issue, mainly due to the kui-tan score requiring human eye type and regular hair type. Steadily balancing the score to allow human, half kui-tan and kui-tan races to have distinctive divisions is definitely a challenge.
I've made an adjustment for the next release that should make the "penis with at least two testicles" score to only count the character also has the "'Nuki Nuts" perk. So if your character ever adopts that perk, they will be categorized as a "half kui-tan" again. Hopefully this doesn't offset other characters who were already half to then become human or some other race.