To further my point on this, you have this meme about Cupidgender. A xenogender that you yourself say is invalid (and I agree with you).
But here’s the thing. That Cupidgender thing isn’t a joke. That’s a person unironically saying that’s their gender. It’s not like my Diet Coke.
But at the same time, they’re both just as ridiculous. And those 2 are also as ridiculous as Arithmegender, or Aliengender, or Orbgender.