But historically people have lived as if they were a man/woman when they were born a woman/man to different degrees
but this such a narrow, gendered view. Yes, some people took on the full disguise of the opposite sex, like James Barry, but for an ulterior motive.
Charlotte Brontë objecting to the restrictions and expectations placed on her as a woman and arguing she should be free to learn, write and be taken as seriously as a man would, and going on to do so, isn’t “living as a man”. It’s refusing to conform to gender stereotypes, and wanting to dismantle and oppose them, so that all women can have more freedoms and be respected and so on. And ideally the same should go for men so they are less restricted by unnecessary limits.
saying “no I won’t spend my life knitting and cleaning and birthing because that’s what women are expected to do” isn’t choosing to live as a man. It’s choosing to live as a freer woman. If you just jumped into the stereotypes expected of a man to avoid the stereotypes of a woman, you’re embracing stereotypes. That is not what 99% of gender non-conformity is.
I include myself in that. I was a short-haired girl who loved tree climbing, airfix, trousers etc. but I wasn’t a boy, nor was I embracing a boy stereotype- I was just me. I also liked drawing, sewing and art. I just wanted to do what I liked without restrictions. These days I’d have been told I was a boy and needed body parts cut off and praised for being wonderful and special if I went along with it.
can you really not see the problem with “living as a gender different from your birth sex”? It strongly implies these gender boxes are appropriate and good, and that everyone who isn’t your special non-conforming self should stay in them.
the aim should be to open up the boxes so people are free to be in or out of them to the extent they like. Gender is a whole range of cultural stuff that changes over time and from place to pace - it isn’t innate. It’s just as bad as if you expect people to behave in a particular way and have particular likes and dislikes because of their ethnicity, age, disability etc.