Not surprised to see that OP has not managed to answer some of my suggestions:
Why isn't she asking all the straight women on Mumsnet to get the opinions of their husbands about the idea of running their fingers down the stomachs of a TW and running up against something solid in the knicker elastic?
Is that turning any stomachs yet?
So straight men are allowed to be repulsed by male bodies - because the OP accepts their sexual orientation is exclusively towards women - but lesbians are not allowed because it is 'absolutist.'
Or just painful for TW to have their sad illusions demolished.
The OP's delusions are clear in the post - that a lesbian might talk to a TW in a social setting and not KNOW immediately who it was.
That the lesbian has no right to reject the TW - most likely at a distance of 100 metres.
I've been in large settings of lesbians over the years, big groups who've dined out on their repulsive early almost mandatory experiences with men. It's something like a rite of passage. We mostly have to pass through the Dead Marshes - those swamps near Mordor - to get to the delights of women.
In these circles we are always jealous of the Gold Stars - remember in the L Word, Shane and Carmen were Gold star - alphas? Just got a lucky pass over the Dead Marshes and started out with women....
And years later along come 'Cis-gendered' lesbians to tell us we've been deluded all these years. That we don't know ourselves well enough to understand our own sexual orientation?
When I told my straight male flatmate about our jealousy of the Gold Star lesbians, he said 'Ouch'! Because he didn't like to hear the truth of the way we feel.
I told him that 1 minute with a woman was worth more to me than 10,000 years with any man.
Finally I told him to imagine kissing a bristly chin, and added a bit more gruesome detail - and when he was begging me to stop, I told him that was the way I feel - I feel about dating men the same way he feels - it's our shared sexual orientation.
Then he became a 'Lesbro' - a cool old fashioned term for a straight man who completely gets Lesbians and can hang out with us - the male version of the kind of woman who used to hang around gay men and be comfortable with that. He gave me dating advice; picked up the pieces after disasters and helped me get back out there. I could return the favour. Because we both love and desire women.
That camaraderie of loving women.
He got it.
But the OP just never, ever will.