LogFAQs > #986272016

Per reddit, so take it with a grain of salt:

It was a style choice for a very good reason. Humans are all animated in twos, the demons in ones. This made the demons movements different, more fluid and ethereal than the humans. There is a scene where one of the hunters sings a yearning love song with one of the demons, she herself is part demon and is animated in ones as they sing showing that she is not rejecting her demon side in the moment. Oh, and animating on 2s with computer generated animation saves no money as the frame still has to be rendered

So if that is accurate then a lot of the variation in frame rate is demon vs human, though I feel like all 3 of the hunters get some high frame rate treatment during action sequences? Not 100% clear, but I can make myself adjust to the frame rate within the first minute so it isn't a big deal to me one way or the other.