Centaurs are not 50% horse. They have 75% of a horse, and 50% human of a human body, smushed together to create a mammal that’s approximately 2/3 horse, and full of redundant anatomy. Two torsos and 6 limbs like an insect.
So then YOU do the math!
And while you’re at it do the math for human x centaur and don’t forget to show your work.
Point 1: use the Harkness test to determine if it’s bestiality or not