Sexuality is weird. It's a strange subjective thing formed by some combination of biological makeup and cultural pressure, and forced into a finite list of constructed identities. In our current political climate, it's advantageous for those of us caught on the wrong side of acceptable to cling to a simple narrative: we're born this way, we can't change, for the love of God stop abusing children by trying to "convert" them into something they will never be. I have no reason to doubt that most, even almost all, queer people actually feel this way, that their identity is innate and immutable. But, as this book points out, there exist people who stubbornly refuse to accept the "born-this-way" story as their own.
I'll admit that a lot of these stories seem like they'd become more comprehensible from some allowance for non-monosexuality. Bisexuality is brought up a few times, but most of the people interviewed deny it, often because they don't think it's actually a thing (ー_ー). So the book's a bit dated, bi erasure was still a huge thing, and sexuality was largely viewed in terms of shoving people into a "gay" or "straight" box and thinking that exhausted the possibilities, forming an overly simplistic, naive binary with nary a bi. But just realizing that a lot of these people may have had some underlying bisexuality and just "committed" to "one side" so to speak doesn't exhaust everyone's self-reported experience of being queer. Because for everyone who just didn't think that being bisexual was real or possible, there were others who vehemently denied ever having any sort of non-monosexual attraction, and were still able to choose queerness over their "starting" sexuality.
I wish I could draw any sort of major conclusion from this, but the book couldn't help me there. Just an observation that self-reported queer-by-choice people existed, a bunch of individual case studies, and reports that stubbornly refused to fall into any of the queer narratives I knew. This stuff is bizarre.