Pansexual isn't a gender, it's a sexuality. It means that instead of thinking "I like women" or "I like men" or "I like non-binary or genderfluid people", we just think "I like people". We don't care about genders.
Tell that to the mushrooms, whom various species are discovered to have over 23,000 different sexes!
here in case ya want a source: https://www.discovermagazine.com/why-this-fungus-has-over-20-000-sexes-523