Ultimately, all in-groups are decided by the consent of the majority of members, since everyone will self-select in the end: those who disagree will leave, those who begin to feel excluded will leave, those who feel unwelcome won't join. You can factor in leadership change and continuity as an additional complication, and the names and labels attached to the group will change, but the phenomenon remains the same.

Societally, we have recently gotten to the point of being able to talk about the importance of having spaces where historically marginalized groups can forge a shared sense of belonging and build up the social support structures that historically less marginalized groups have long enjoyed, but I don't believe we've gotten to the point of being able to have a reasoned debate about edge cases where different groups overlap in some ways, yet diverge in others, along axes some might find incompatible.

I also don't necessarily think that this is for the group leader to solve: this is a process that will take years of successes and blunders, and cause everyone involved to tackle an additional layer of delicate subjects that they may not be ready for. It appears that the group leader has laid out their vision, so for now, the points you raise will likely be addressed in a distributed fashion, in the minds of every member or prospective member, as time goes on.