I think that the point that having an official role within what is ostensibly a women's health organisation opens a lot of doors is an important one. It sounds as if the founder/Chair may have already seen it as a vehicle for promoting her particular beliefs about endometriosis and her loyalty to the gender bollox.
As well as providing some personal validation for Steph, it will also help Steph have access to various women's health networks and NHS fora. Other charities are often more tied up in service delivery or supporting their client group and don't have time for endless multidisciplinary or multi agency meetings. Before you know it the niche views of Endometriosis South Coast would be mainstreamed.
I understand the argument that this is a tiny charity, but that doesn't mean that they couldn't do a lot of damage - especially since so many of us women have been socialised into being nice and inclusive (and, it seems to deny reality). It might also be more difficult to be seen to attack a larger, established charity, or something like a Rape Crisis Centre. I think Emma did a brilliant job and it will have made a lot more people think about the underlying issues and principles.