This is a comment on Changing a Categorie of a page after it has been created, posted by WikiAdmin at 04.07.2020 12:08

View source for Re: Do not save parent category automatically along with the selected sub-category

Is the selected category a sub-category? If so then the parent category get automatically selected along with the sub-category, regardless if the parent-category is not selected in the form. This behavior was  back-ported along with to category handler.

This is of course not consistent with the selection made in the form. We can change this behavior so it selects only the chosen categories.