I've "discussed" this on Twitter with various TRAs who tend to say "oh I didn't tell anyone or do anything until I was a teen because my parents were so awful".
So this means they did not meet the diagnostic criteria for GD until they were a teenager.
But they now say that yes they are and always have been gender dysphoric i.e. meeting the diagnostic criteria - the criteria which include obligatory visible expressions of dysphoria/gender non-conformity in order to be met in full.
Thing is, you can't have it both ways.
You can't have diagnostic criteria which you meet now, didn't meet then, and then complain that the criteria are wrong. Either you go by the criteria (and you are now officially GD) or you scrap the criteria entirely (and go for new ones which, according to these TRAs, would probably be entirely subjective - no, that is not going to wash in the DSM).
However personally I would argue that the criteria do NOT indicate gender dysphoria in most young people - because having long hair (as a boy), having friends of the opposite sex, and playing with non-gender-stereotyped toys should NOT be indicators of gender dysphoria.
As I'm not an expert, I don't really know what SHOULD be in a set of criteria but at a minimum I'd say it has to include some expression (as in, expressed to another person) of dissatisfaction with the child's actual body. And I don't think any of the stereotyping stuff should be in any more. And I also don't think that leading questions should count (i.e., if a boy says "I want long hair" and the parent or therapist asks "do you think you might want to be a girl?" that should NOT count as expressing dissatisfaction).
So we are left with: child does not express the wish to physically transition/dissatisfaction with body. Adolescent does express this wish. I think that's at the core of this and there need to be studies of how prevalent this is AMONG THOSE WHO EXPRESS GENDER DYSPHORIA AS ADOLESCENTS.