OK. I'll engage then. No one wants to be Anthony Watons, least of all Anthony Watson, probably.
OldCrone
I'll start by saying that there are 3000 or so people on the UK are who are legally women. I disagree with TRAs who say sex is a spectrum (it's clearly a binary with a few exceptions.) I also think sex is a real, physical category. Humans a sexually dimorphic.
So what does it mean when someone has female anatomy, but identifies as a man? It all comes down to gender identity. GC feminists think it's akin to a religious belief. Psychologists and most national and international health organisations and trans gender activists think it's a real thing, like sexuality. You can't point at it, but it's there. People who don't have disorders of proprioception don't even know they have it, and yet proprioception is real.
If your gender matches your sex at birth, you won't feel any conflict between your gender identity and sex, and because of that, you will know you are woman without any conflict. That sure and certain knowledge is your gender identity. Equally, a XX person who is certain they are a man, has a gender identity which conflicts with their sex at birth. Psychologist think that gender identity is established at a very young age - less than four.
Gender identity is not "believing" or "deciding" you are a man, it's knowing. Wanting to express yourself atypically is not the same as knowing your own gender - some people's gender expression does not match their gender. Often, to be accepted, transgender people express themselves in a fashion typical for people of their gender, which is not to say such expression is not sexist.
So, if a person's gender identity does not match the sex identified at birth, they are transgender.
Now, if you think that gender identity is just a belief, then you might be angry at me for saying that you have one. I can't really help that.