You mean something like this book? https://www.goodreads.com/book/show/220289.Do_Princesses_Wear_Hiking_Boots_

Yeah, my take on this letter is that their enforcement of gender neutrality is just as rigid and problematic as society's enforcement of femininity - with the addition of "not only is society's enforcement bad, but we're going to make sure that you think everything feminine is bad, regardless of what it signifies or how you interact with it." Way to stifle a kid, parents.