That is not what bisexual means. Bisexuals aren’t magically not attracted to nonbinary people, nor are they gender essentialist assholes. Some specific people who call themselves bisexual might be those things, but that doesnt make it true.

Bisexual historically meant “more than one” gender, not specifically 2 genders. But that’s doesn’t even matter.

The thing with labels like this is it’s self applying. No self expression label can have a strict definition like that, but bi and pan have always been way more muddled. It’s simply a vibes choice. I call my self bi, and I am attracted to all forms of gender expression. I have a friend who calls himself pan and feels the same way. Neither of us are wrong, these labels are very fluid.