While I understand that some people don't have a problem with who uses female single sex spaces, other female people do have a problem. It is not just about safety, it is about privacy too.
Toilets are not just used behind a closed cubicle door. There are quite a few aspects of female toilet usage that happen in the public space, or even now still occur with a toilet door jammed open.
Well from my personal experience here is a list.
I have had to use the toilet while having a pram / pushchair jammed into the door with groceries.
I have had to have my mum use the public toilet because the disable toilet was not available and had her wheelchair jammed in the door because I couldn't leave her sit to move it and shut the door.
I have had breastmilk leaks / children's vomit / food spilled on my clothes and needed to have an unbuttoned top to dry the top under the hand drier.
I have come across other women quite regularly washing out their tops or their skirts etc and drying them enough to put back on .
I have friends who have miscarried in toilets and needed assistance and for that to be female people to make it more comfortable.
If you as a female person have not experienced these issues, that doesn't mean it is not happening. I am glad that you have never needed to do this things, it is uncomfortable and can be quite humiliating. But at least, in a female only toilet, it is a little better.
I think when people think of toilet usage, maybe they have never had to use the toilets in any other way other than behind a closed door. But the needs are still there and they are real for many female people to be able to engage in public life.
By the way, I posted this earlier in the thread and a poster accused me of 'exposing myself' because I had to use a toilet with my child's pram jamming the door open. This is the level that people who prioritise male people getting access to female toilets will resort to. If that poster was a mother, they obviously lived a very privileged life where they either had toilets for parents provided, or never once had to use public transport to get supplies for their family while having no choice but to shop alone. I wish that all mothers had that privilege, but we don't.