Copied this excellent comment, which I agree with, from YT comments (user Carmen McNew)

What I noticed when I watched a special on a Swedish family raising "Theybies" is an "unconscious bias" to purposefully steer the child towards opposite sex identification. The child, they acknowledged, was biologically a boy. But, the caretaking partner would take the child shopping and light up around dresses and tell the child how pretty the dress was and ask if he wanted it. You could see that his desire to please his parent factored into his willingness to express an interest in the dress. I believe the unconscious bias of these non-binary parents is to steer their children to like and be interested in toys, clothes, and activities generally associated with the opposite sex. Since these parents do know their children's sex, they, perhaps unknowingly, get excited and show preferences for opposite sex activities in an effort to reinforce their belief that gender is fluid. This social experiment is, therefore, already doomed to failure from the moment someone has to change a baby's diaper but wants to push a gender bending agenda.