You are over-reacting a little here. This book is not a great candidate for something actually sexy. The characters try something sexual and find it really doesn't suit them and they stop. The POV character has massive dysphoria around being touched directly down below and so it's hardly glammorizing sex acts. Rather the entire thing is framed as a complete disappointment.

A lot of the focus on "well not MY child" is being used to perpetuate this book ban nonsense in public libraries and other spaces where general collections are for all ages. Just as you struggled with the mental health issues around being a sexual assault victim at 14 and likely there wasn't a lot of materials on offer to help guide you trans kids most often start feeling body based dysphoria at the ages of 11-14. Those kids are left often with a fairly nebulous view of the future where they might not have access to healthy adults who can help understand what they are going through and give insight into what their lives might look like when they grow up. Their fears about ever being able to feel comfortable in their sexuallity is valid when they might be having severe reactions to their own sexual development.

What I find particularly interesting about all this is this book is essentially one where a person with fairly intense dysphoria depicts what a fully complete non-surgical transition looks like where a purely mental coping strategy is employed. I would have thought this book, in a discussion that regularly centers around prevention of surgical transition would highlight this character who finds ways to carry on outside of a medical model... But it doesn't. Because trans people's problems and solutions are always treated as taboo and perverse regardless. The answer we overwhelmingly get is just "Well, you are just supposed to be permanently unhappy. " which isn't exactly a beacon of hope.

Your kid might not need this book but I was desperate for something - anything like this when I was that age... I grew up in the 80's and 90's where I had no bloody clue what was happening to me and why everyone else seemed fine while I was having routine anxiety attacks about puberty that made me think I had heart problems and my issues would likely be solved for me by me dying before I ever grew up. Sex ed leaves a lot of pressing trans issues at a critical age unaddressed and while 11-14 may seem young it IS a crucial turning point in puberty which doesn't exactly go well for a lot of us. Basically by the window of time girls get their first period there's also young trans kids in complete crisis.