There's a story on the BBC website today www.bbc.com/news/health-63331805
I read the details, and after signing up, you can withdraw fully at any time.
So I signed up, went to the questionnaire, and the first question used the wording "sex assigned at birth".
So I went to the "withdraw" page and clicked "fully withdraw". To do that you have to phone a number. I did that, and the agent at the other end said my withdrawal would be noted and I would receive a confirmation email. She then asked why. I told her that my sex was observed at birth, no-one assigned it to me, and that a health study that didn't recognise that fact was not based on biology and was therefore not worth taking part in. She said my reason would be passed on to more senior staff. Good.