The thing is that there are healthcare implications of all this. If I went to A&E as a self defined "male" with stomach pain, it might have taken them to figure out that I'd got a burst ovarian cyst.
Especially if every HCP was expected to go along with my delusions that I was biologically male.
Also in the case of fathering/mothering this could affect genetic investigations for disease in a child couldn't it? Can't some genetic conditions only be passed on by the male parent and some by the female?
Imagine the appointment with a geneticist "so you are little susie's...?"
"Mother" "okay, well the chromosome analysis has shown...erm...well..."
The trans community seems to be demanding that HCPs ignore basic biology and treat them according to their chosen sex.