That video was 9 minutes and it summarized the results of several studies done in the last 40 years. Those studies were done in an effort to better understand the phenomenon of Sexual and Gender Minorities.
Please consider the following questions:
What appears to be the largest influence on the sexual & gender identity of a person?
At what period in a persons development does this influence take place?
At what period in a persons development does the result of this influence become noticeable?