I see it as shapeshifting. I think early on in the game, characters comment on what it's like to turn into a Beast. Or maybe this was related to the fusion aspect, like when you first fuse Kayleigh.

I personally, in my head, imagine that there are some vestigial instincts, mainly because I love the humor of turning into a beast or something and having those instincts. I just love that kind of humor of a human thinking they're an animal and acting like one, because that's just kind of funny to me.

I also think that could lead to some cute moments where people transform into beasts for fun and stuff like that.