Julian is a mermaid?

[Mybrowneyedgal]

A family member bought this book for my children. I was initially wary because of the reference to mermaids but felt pleasantly surprised once reading it as it appeared to challenge gender stereotypes. Dd and Ds responded well to the general message- you can be whatever you want even if it's outside of stereotype.
However I've looked at reviews and there's references to Julien being a trans child? I can't see how this is evidenced within the book and it worries me this messages is interpreted as being about a trans child- Julian has to change gender in order to be able to dress as a mermaid?
I feel really confused and disappointed, have I missed the point? How can I teach my children to not feel like they have to conform to gender stereotypes if they're constantly being given the message that if they don't conform they must be trans?
I suppose I am just venting at this point but I feel really confused, I want to do a good job of raising my children to feel comfortable in themselves but its becoming more difficult every time I try to talk about gender conformity.
Any advice would be welcomed, also did I misunderstand the books message?

Maybe it refers to the fact that Julian is a mermaid refer than a merman?

I haven't come across this book, but i do have children so I had a quick look on Amazon to read the publisher summary

In an exuberant picture book, a glimpse of costumed mermaids leaves one boy flooded with wonder and ready to dazzle the world

While riding the subway home from the pool with his abuela one day, Julián notices three women spectacularly dressed up. Their hair billows in brilliant hues, their dresses end in fishtails, and their joy fills the train car. When Julián gets home, daydreaming of the magic he’s seen, all he can think about is dressing up just like the ladies in his own fabulous mermaid costume: a butter-yellow curtain for his tail, the fronds of a potted fern for his headdress. But what will Abuela think about the mess he makes — and even more importantly, what will she think about how Julián sees himself?

Sounds lovely!
There doesn't seem to be any predictable plot twist like ta daa so now the boy is actually a girl in there.

There's the niggling bit
even more importantly, what will she think about how Julián sees himself? well I don't know what she thinks because I havn't read it, but why is it so important what an adult thinks about a boy dressing up and seeing himself?

It is a beautiful book but I agree it's a bit strange how Julien is nervous to tell his nan he wants to dress up... like the sex workers/drag queens they see out and about. I definitely think you can read it as a sweet and innocent tale of imagination. But I think the author's intention was that Julien is trans and his dressing up is to be seen as a massive transgression which luckily his family supports.

Apparently intended to be about transgender identity, yes:
www.theguardian.com/books/2019/sep/11/i-am-proven-joyously-wrong-picture-book-about-trans-child-wins-major-prize-amid-moral-panic

Just came across this piece: booktoss.org/2018/09/24/trans-people-arent-mythical-creatures/

Good grief.