The answer Dr Stock gives in Material Girls is that there is such a list and we look for most of the attributes on the list. So "lion" would be something like big feline, has mane, hunts and eats meat, has tail, etc." and that encompasses a wide range of variations - Asian lions are lions just like African lions even though they look different, a lion that lost its tail is still a lion because it still has most of the attributes on the list. A tiger has most of the qualities on that list but still isn't a lion because we know "not having stripes" is an essential part of being a lion. Penguins are still birds despite not flying because they have most of the attributes on the list. But mosquitoes who do fly aren't birds because they lack most of the other bird characteristics (feathers beaks etc).
So your bf probably thinks that the list of what makes someone a woman is something like "female biology, long hair, wears makeup, has female-coded first name". Transwomen don't have the first but still have enough of the characteristics on the list to be "read" as women in his opinion. Whereas you understand that names, hair, makeup etc are not inherent characteristics of womanhood - probably because you have enough feminist theory to understand things like the male gaze etc.
So, do you love the guy? If yes I'd ask him to gender you every day, and when you are wearing trousers and no makeup the answer really ought to be a male gender id. If he's straight he cannot be attracted to you any more as you identify as a man for that day (make him call you Dave for good measure). Give him pictures of yaniv etc and suggest them as alternatives if he's feeling horny as they do perform "womanhood". Basically make him do the lion vs tiger test on you - if you have stripes, ie a uterus, you just cannot be a lion, ie a bloke. Even if you develop a taste for antelope. Women who don't or can't get pregnant are the penguins in this scenario - not being able to fly just doesn't make them mammals or snakes or insects. They're still birds because they tick every single other box for birdhood. Make him come to that realisation himself. Be dead serious about it, gender ideology is no laughing matter. He really ought to readjust his mental list of what makes a woman...
If you don't love him, dump him. It's a canary in the coal mine issue for me. If a man doesn't believe an actual woman telling him what womanhood is, he's a mansplainer / misogynist. Life is short, there's plenty more fish in the sea.