Who knows, but you certainly don't pass the intelligence and knowledge of science tests. You've conflated three separate concepts into one and then argued on the basis of one of those concepts that the others don't exist. Way to use fallacious reasoning, there.
Now, I'll explain. There are three separate yet related concepts that you've smashed into: sex, gender identity, and gender appearance. Your sex is immutable, and by and large, a binary proposition. Not always though, there are genetic and physical conditions that make a person neither one sex nor the other, or maybe a combination. It's hard to say. Your sex is basically the configuration of your genitals and genetics.
Gender identity is how feel about what gender you are. Do you feel like a boy or a girl or neither. This is separate from sex. There are plenty of studies establishing that sex and gender identity are different things and may not align. Since it is not reasonable to ask to see a person's genitals and genetics, it is not reasonable to base your pronoun use on those things. Therefore, out of respect, one should use the pronouns a person asks to be used for them. Your do this because to do otherwise is an insult and walking around insulting people makes a you bad person who ought to be shunned as an asshole.
Gender appearance is how a person presents their gender to the world. Generally, for mental health reasons, a person is advised to align their gender appearance with their gender identity. Sometimes this is difficult. Here are the rules for pronouns: use the male or female pronouns that match a person's gender appearance unless they tell you otherwise. If there's any question on their appearance, then use they/them until told otherwise. This is purely a respect issue and find otherwise makes you an asshole.
There's plenty of science backing all this up. There's a recognized disorder called gender dismorphic disorder that people can suffer from and the treatment is too transition your gender appearance to the gender you identify as. Sometimes this may even need to involve surgery, but this is becoming less common over time for bottom surgeries and more common for top surgeries. When this disorder appears in children, puberty blockers are used for a few years just to make sure that child really suffers from the disorder before making any medical changes to their body. It makes sense when you think about and seriously reduces mortality from suicide among young trans people. Now you know.