Commit d8b1b79ea423ef3391c34f63aa382fd6bad6597e in core (change Id44d566a7ca35a1b9579d0c0e947877c980b0686) finally fixed the bug where a redirect to a category would add the redirect page to the category.
This now needs to be cleaned up in Parsoid as well (this was a bug-compatibility thing we added, we now need to remove it). See https://gerrit.wikimedia.org/r/221880