No one should be told there is something wrong with who they are....
No one should tell a child/adolescent their belief they are in the wrong body is true because that implies there is something wrong with the child/adolescent.
The Finnish expert in adolescent gender medicine, Dr Kaltiala reported on this (my bold).
Asked by Helsingin Sanomat what she thought of gender self-identification for minors—a proposed element of the new Finnish law that did not ultimately pass—
Kaltiala emphasized that it is “important to accept [children] as they are,” but this means neither pressuring a child to conform to behaviours traditionally associated with the child’s sex nor “negating the body” by confirming that the child’s gender self-identification is real. “In either case,” said the psychiatrist, “the child gets a message that there is something wrong with him or her.”
^Evidence from a combined 12 studies to date demonstrates that when children with cross-gender or gender variant behavior are left to develop naturally, the vast majority—“four out of five,” according to Kaltiala—come to terms with their bodies and learn to accept their sex. When they are socially transitioned, virtually none do.*
https://www.tabletmag.com/sections/science/articles/finland-youth-gender-medicine
Dr Riittakerttu Kaltiala, a psychiatrist at Tampere University, founded one of Finland's two pediatric gender clinics in 2011.