I think they [or you, I did not see the video you're referring to] are conflating concept of gender with sex, that's why their claims seem to be confusing.
Swap "gender" in the statement "Only a minority of children who experience gender atypical thoughts live to adulthood or adolesence having the same atypical thoughts." to "sex" and it makes hell of a lot more sense. Because... how can you have "gender" atypical thoughts if gender is only a concept and we are who we are, right?
there are 2 genders, though. Not to confuse my statment with "infinite genders!".
Cheers