Why does it even matter if the dev made it or not? For those it into incest even shitty patches that simpy change titles (the enitre story is a bit more work) are better than nothing, who cares who made it. Strange that a pirate site gives a shit what developers think of the tags it attaches to their pirated/leaked game. Of course if it was written with incest from the get-go it would obviously be better than a 3rd party patch, but thanks to Patreon's bullshit there's plenty of that disappointment to go around.
That's like saying if I draw a mustache on the Mona Lisa its somehow part of the work instead of vandalism. The ARTIST determines what his work is about. He sets the boundaries, the scope and the subject matter.
Some random person throwing a patch doesn't change the original work. Just because you are clearly obsessed with one particular fetish doesn't mean it should retroactively change the story. It's not even an in depth mod, just a few lines of dialogue. What if I built a mod that had one frame of low quality picture showing the MC murdering and eating Lilith? Should the genre change to snuff and vore?
This game isn't made to have incest (at least, not the kind you are looking for). It's not a part of it. It doesn't work with the narrative and for all of us (probably the vast majority) who don't download the patch, its non-existent. The tags reflect reality, not your personal preference.
That's why it doesn't have the tag.