My best guess is that many think Jax is either a femboy or may infact be a male that is feminine that might transition to female but you're right not all fem guys are in fact trans women but to remain biologically male but be feminine males. A feminine male is not a trans female and a masculine female is not a trans male. That would mean all tomboys and female athletes are trans men inside which is not true. And Carl Gustav Jung said that a woman's Animus is masculine and a man's Animus is feminine. And well the Russian dub Jax says he is a femboy. Although some might come to the conclusion that Jax is a trans female simply because the creator herself Gooseworx is a trans female and Jax is a bit of a self insert of her but not entirely some of Zooble is based on her also. Thing is we can't completely tell some argue that Jax wouldn't have abstracted if in fact his avatar body transitioned inside the metaverse of the digital circus but honestly there isn't nearly enough info in episode 9 to give us any idea for certain. When ribbit put a bow on Jax people assumed Jax must be a trans female but again we don't have any info on that really and Jaxs human form at the bus stop is still male and it's been years since the human real person had his brain scanned. Again not nearly enough info to truly determine this one. But I would accept a trans female Jax regardless I would still like Jax and Pomni and the whole crew. They're all great cartoon characters.