A lot of patches work by just changing a variable in the game which triggers different text to appear or names to be used. I don't support incest content in any way in the game, so the patch has to override entire scenes in order to display different text within them. Which means if I add a scene specifically referring to Katie as housemate or w.e then the patch author has to replace that scene with one that says sister.
Which means older versions can work with newer versions of the game, but if I've added new scenes that call Katie house mate, that won't be changed without the patch being updated.
TheImage