SarahCarer Well glad you've got through the rough. Yes the situation you highlight is one possibility and the links with GID and ASD are very well recognised. There are countless references as I'm sure you know www.researchgate.net/publication/273639503_Brief_Report_Autistic_Features_in_Children_and_Adolescents_with_Gender_Dysphoria
I don't think that explains all gd in children and I don't think it accounts for all of the increase either. Though clearly there is a connection sometimes.
You say sexuality is entirely biological and gender identity is entirely socially constructed. I don't believe that. Most mental health professionals don't either. I'm not saying blue brain pink brain, but I do think gender identity is a mixture of genetics, biology, biochemistry, environment, society and culture. The human brain is sex-hormone sensitive, both during development and as an adult. There are some differences between average male and average female brains in terms of structures. Sexual behaviour is a 'behaviour' and that can be determined by brain physiology so why would we think that no other behaviour is either?
Sorry I don't believe there is no connection at all between gender, gender identity and sexuality. I think there is. Not a totally rigid, inflexible and always predictable one. It is within the context of the great and fabulous diversity of human experience but nevertheless there is some connection.