Yes but being gay is simple. Most people are attracted to people. Attraction is almost universal - what differs is who you're attracted to, but you all feel the same. *(Asexuality I would say is exempt from this in that your feelings aren't the same)

Being trans is not simple because you specifically feel different. This alone makes it harder to understand than being gay. On top of that, society pressures each sex to conform to gender norms and there's lots of kids that specifically "rebel" against those gender norms. Plus kids brains aren't fully formed and don't usually understand consequences in the same way as adults.

With all of that it makes it much harder to recognise a mature child that really knows they are trans vs a child who doesn't mind the sex they were born as and is reacting to a myriad of social problems instead.