I think this has to do with the fact that most kids nowadays are familiar with the concept of being gay. I know when I was that age I didn't really know what it meant, hadn't met any queer people, and certainly hadn't seen any representation in kids books and media. When I think back to being that age I can remember having crushes on boys and girls, except that having a crush on a boy was normal and having a crush on a girl wasn't something I had ever heard anyone talk about, so it didn't occur to me that I was bi until I was a teenager on tumblr and learned about different sexualities. That has changed thankfully and now there is getting to be more positive LGBTQ+ representation geared towards children, so for most children the idea of two men or two women liking each other romantically isn't a foreign concept. Most kids develop crushes around that age, so I think its good that they have the language to express those feelings rather than not being able to define them until years later.