On the contrary, that has nothing to do with the LGB. Shrier believes the T concept, specifically, is a social contagion like anorexia.
Their comment did not attribute to Shrier any view of sexual orientation. People who consider gender identity illegitimate and people who consider sexual orientation illegitimate overlap.
A wall street journal opinion columnist - Shrier- with zero medical training wrote a book to create a moral panic in the public about trans teens, based on the discredited ideas from Lisa Littman's ROGD "research", where in this case the word "research" actually means: reports from parents recruited from well-known anti-trans websites.