It's most likely not a game creator or creative in any way, but more likely a former fan who's just angry at Mofu and trying to harass them by doing false reports that characters look like minors to Itch and other platforms. Then they lie and claim on other sites the game was taken down because of copyright laws (that's not how copyright laws works, especially when Mofu isn't even making any profits yet on the game).
The person claims to have designed a bunch of characters in the game, despite the fact the person doesn't even have the talent to draw them, let alone make a Hentai game themselves. In reality, all they've really contributed were some ideas and really bad/rough drawing at best, which is complete joke that anyone can do and is in no way copyrighted material.
If this was truly a case of copyright infringement, millions of independent or doujinshi artists that make profit over using actual copyrighted characters in Hentai parodies would be out of business, or they'd have to seek approval from big companies to use said characters (no one does this cause it's ridiculous and no big company would approve to see their characters used in such ways). This is not the case though, since even if those characters in Futakin Valley are copyrighted, (they're not) they'd still fall under fair use, as it's still considered it's own unique creation and done in their own style. That's why doujinshi artist can use actual copyrighted characters without approval and make profit without legal repercussion.