Single use bathrooms are not safe for those who then have medical issues while using the toilet, or are being attacked in the toilet.
The gap underneath the door is there for a reason, and that reason includes being able to see a person who has fallen onto the floor or if a person is being attacked.
here is my personal list of things that I have had to use the female single sex toilets for:
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.
The cleaning up of clothes for breastmilk leaks and for other spills has happened to me in a work situation. In fact, it has also happened in a conference situation. One of my friends miscarried at work.
At work conferences it is not uncommon to find women drying their clothes under the hand drier because they have spilled something on their clothes.
That you (a general you) have not experienced these issues doesn't mean they are not happening. I am glad that some people 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.
And no. Waiting for things to be dried if a cubicle has a hand drier is going to cause congestion and therefore stress for a person having to clean and dry themselves off in a mixed sex environment.