It was listening to the BBC interview with the schoolchild (its on another thread so I'll have to go find it) and I had a lightbulb moment.
The child (born female) was primary school age and asserted that they should have access to both toilets because of identifying as non-binary. That this was what was 'wanted' and 'should' be granted. That rather than being neither boy or girl, was both. This seemed to be clearly reinforced by the mum who also referenced online groups as a source of information for the child's grandad.
Although its a child speaking, the narrative seems to have been absorbed from adults.