I think this is exactly why the SC judgement was needed - it isn't possible to segregate on gender because the term is not meaningful. That's why they had to stop the whole subgroups of sex class with different needs.
As an example, let's say you advertise an Inclusive Walking Group.
I assume that your intention might be that it is for women and trans women.
You might have in mind that you would want to include biological women, trans women with GRC and self ID trans women?
How might you control who can/cannot have access?
You can't ask for a GRC.
Passports or driving licences won't help much because they may or may not accord to the identity in which that person is living.
You can't go on appearance - because there are people in your chosen group who might look stereotypically male (either because they are non steretypically female, or male or because they are trans men).
I think to run an inclusive group, you would have to be specific about who you wanted to exlude - if that isn't a weird concept...?