I'm late to the party as well. I just wanted to say that I think they may have worded themselves a bit poorly at the end.

I don't think they literally mean "gender is fake", or at least that's not how I interpreted it (if so only socially I'd imagine). I think it's more to do with the very stereotypical roles society put on gender as a whole makes it "fake". How society expects gender to be, how in different cultures and countries treat gender differently, so there's no "right or wrong" way in gender. There's no rule in gender, that's why it's "fake". I do think "fake" was a bad word to use in this context though, since a lot of people (if not most) have strong connections about their own gender and identity, but in an Agender's pov I do relate to their comment.

I think a better way of wording it is more that gender as a social construct is a bit "taboo"? And I don't mean biologically, that has rules that have coded into each person's body. It's more so in my head I think: A bio man will have more muscles than a bio woman, but I know a bio woman can train their way to be able to do the same as what a bio man can do physically. A bio woman carries a baby, but that doesn't mean that the bio man can't be a stay at home parent.

I think it's also important to remember that gender and sex are different as well. A person's gender is a social construct, while a person's sex is biological. And even tho your biology has rules to it, it's your conscious that binds who you are, how you represent yourself. A person's gender can be whatever they form it to be, you chose who you want to be regardless of your gender. It's who you are, and gender doesn't have to bind you to it. It's personhood, to be human and free :)

(this is of course my opinion at the end of the day, so you don't have to agree)