The fact that superficial perception can be tricked does not change the reality of human biology. People think spiders are insects, but that doesn't make it so. People have mistaken me for a man, that does not make me male. It's honestly astonishing how many trans activists need to have it explained to them that holding patently false beliefs does not make them valid just because you believe in them.

I will also say, I have continuously been able to tell who's male or female in online trans spaces solely by their very typical gendered socialisation. That perfectly demonstrates why gender validation is so problematic and even straight up dangerous. Saying someone is male or female based not in whether they are male or female but solely based on hearsay or superficial appearances ignores the actually real gendered socialisation that we are all raised with, whether we acknowledge it or not.