I started teaching consent in age-appropriate ways as soon as they started walking. My 2yo already asks not to touch his body when he feels uncomfortable or overstimulated, and is on his way to acknowledging when others say the same to him.
My 6yo has already recounted uncomfortable advances from boys at school, and how she avoided or ended the encounter- First with her words and then with action. I'm well aware that by the time she's 10 she's going to discover adults looking at her in a particular way. There's no way in hell I'm going to let her out into the world without the awareness of that as well as the tools to protect herself from it.
Nonconsensual sex, being one of the ultimate violations of another person, will be well understood. And we're building from the nature of our bodies and others. And next into consent and what that entails.
To your last sentence, I remember being an extremely horny 11yo with no idea what was happening to my body and no one to look to for advice. Sex was a taboo subject in both home and school. I learned some dumb shit from other boys with older brothers instead.
Except per the article this book was not at the school