JB's point about 'freaks' was that if issues like single sex spaces and the medical transitioning of children are fought as single issue campaigns they ignore broader feminist understandings and criticism of the extent of harms caused by male violence towards women including the hate directed towards lesbians.
If success is measured solely in terms of single sex spaces being reclaimed and it not being permissible to involve children in body and life changing medical procedures, that maintains every other structure and mechanism of patriarchial oppression. That was the status quo in the UK, what, 15 year ago and while undoubtedly better than the situation today, women and girls were still prostituted, raped oppressed and exploited in a million different ways.
These aims are shared by various homophobic groups, on the right, left and/or with religious convictions (obvs not all) who, at best, regard gay men and lesbians as freaks of nature. That means that lesbians would have to not challenge/ignore/go along with beliefs and practices that dehumanise them in various ways. They'd be tolerated freaks when they were useful, then untolerated freaks when not.
Yes, some lesbians are fine with this, in the same way that some immigrants are happy to work with or within anti-immigration groups.
JB can't stand most of the Labour party btw. She does jump about a bit in her arguments, I think because she's thought about and spoken about it all so much that she forgets that they're new to some people. I'd recommend reading some of her books, articles, or listening to her podcasts if you're interested in more context.
I felt the same about Helen Joyce. I've read and loved 'Trans' but her concept of market economics that don't rely on some social groups being oppressed was a novel one to me, and not one that she fully explained.