it is part and parcel of a tendency in education toward bringing things into the curriculum that don't belong there
I agree that the information was shared in an incredibly clumsy way which won't lead to true inclusion and may have the opposite effect by othering pupils who share characteristics with those teachers, and causing them great anxiety if they feel they might be encouraged to 'bring their whole self' to school.
I also personally have an objection to declaring that one's identity is gay, as opposed to one's sexual orientation being gay, because it suggests that it's self-determined and self-defined. One's sexuality can only be oriented in relation to others, so it feels artificial to express it in this way.
I also feel that the notion of 'gay' as an identity akin to gender identity assists in the argument that sexual attraction is something that should move with the times and adapt to accommodate heterosexual relationships pursuant to gender ideology, as if it is controlled by the person and can flex as necessary when told to.
And obviously, it would be horrific and completely bizarre if pupils were quizzed on their sexuality and forced to reveal this publicly.
However, if it comes up naturally in conversation, I strongly disagree that it's inappropriate for pupils to know a teacher is gay. As a gay teen myself, it was reassuring to have a gay teacher in my school, and she was the only one who tackled any of the homophobic bullying going on. She also stopped a lesson once because a kid made a sexist comment and she explained why gender stereotypes were a load of bollocks and incredibly harmful to everyone.
And later, as a gay teacher who wasn't out, it was really awkward because teenagers are curious and would pry into my personal life - they wanted to know everything. Obviously I maintained professional boundaries, and part of my job was to teach boundaries to the kids (e.g. explaining why it's not appropriate for me to tell them my address). But had I been out, I would have seen no issue with mentioning a partner.
Yes, OP's DD's situation sounds awful, but not because knowing a teacher is gay is inherently inappropriate for pupils to know - because of the way that information has been conveyed.
Sexual orientation is completely different from gender identify. If OP had an issue about the impact on safeguarding of this material in relation to paving the way for discussions around gender ideology (and the ones I'd be concerned about are listed above) then I can see the tangential relevance to FWR.
But the OP and title seem more concerned about the inappropriateness of knowing a teacher is gay. As if being gay is related to gender or in any way similar to being trans. It's not.