"gender non conforming girls"...
Girls being the important word.
GG have stated that they accept anyone who self ID as a girl. That is about "internal" ID. Gender non conforming is more about dress and style. So, a gender non conforming girl, could be a child born male, who feels like A girl inside, and according to GG is therefore literally a girl. They would not have any concerns about that girl, or any other girl, not conforming to stereotype, so eg they might have short hair and wear clothes that are favoured by boys, that would be fine.