I saw that one a week or so ago, so forgive me if my recollection isn't perfect.
They're mostly talking about the content of her book and the topic is almost entirely about FTM transition. Though they make a distinction between genuine transmen and girls with mental health issues who grasp on to the transgender movement when they aren't actually gender dysphoric. Instead of engaging in eating disorders, self-harm, etc., they're engaging in gender transition to satisfy some need for attention, praise, fulfillment, etc. I dunno.
Citing the supposed phenomenon of clusters of teen girls coming out as trans after contact with trans friends, online activism, etc when there was no indication of gender dysphoria before.
If I recall, there was also some discussion of the danger of blanketing a medical/mental health issue as a civil rights issue making it difficult, if not impossible, to give a genuine professional opinion on the matter that is not properly in-line with transgender activism. Because careers would be on the line. I think the author claims to have spoken to doctors and researchers who refrain from raising concerns, because they're afraid their careers will be ruined due to how fervent the activism about the issue is.