I do have a genuine concern about musclebound, beardy transwomen now needing to be in women's toilets and changing rooms. On a practical level they aren't the same level of threat to women as transwomen are, but two things bother me.
One, my concerns about someone presenting as male being in female spaces are still relevant. I don't know that someone who looks like a man is actually a transman.
Two, how will we deal with them? Legally they're protected from discrimination and harassment. Just as it's wrong to challenge someone with a blue badge because they "don't look disabled enough" to need one, surely a transman can't be challenged and doesn't need to explain themselves when they use a women's toilet or changing room. I guess we could call the police but it would leave us open to legal action if it turned out they were a transman just exercising their legal right (and now obligation) to use the women's facilities.
This is a real concern because what's to stop a man coming into a women's changing room insisting they are actually a transman? Some businesses will be reluctant to enforce checks on genuine transmen because they can't discriminate against them. This means they can't place additional checks on someone claiming to be a transman that they don't check with people who claim and appear to be female.
I think the recent ruling is necessary and sensible in its requirements on segregation around birth sex but I fear that for as long as there is legal protection for transpeople to not face discrimination or harassment there will always be loopholes the unscrupulous can drive a bus through.
I'm not saying they should lose this legal protection of course, it's just I don't see how trans rights are fully compatible with women's rights.