The way I see it, werewolves and other furry/anthro (including merfolk , nagas/lamias, etc.) are recognizably based on bipedal humanoids. Those are safe to use AFAIK. But centaurs are entirely animal below the neck, with a human from the hips up replacing the neck & head. That's probably what he's being cautious about.
Knowing the masses at least a few people will have complained about/reported centaurs to patreon. No idea if anything came of it. I don't blame him one bit for not taking chances with centaurs.