Is it a German thing maybe?
I am currently reading this German book to dd1, who is just seven. The book has received lots of praise in Germany, it is generally recommended for age 8 and above, but there is no mention whatsoever that it would be unsuitable for girls younger than that, and as dd1 is quite mature I decided to read it to her.
In one chapter the class in which the main character is discusses chickens, and the teacher says "eggs are made from chickens having sex, the cockerel jumps onto the hen and has sex with the hen. That's how the egg develops, similar to humans." then a child says "but in humans the man doesn't jump onto the woman." the children laugh and the teacher says "no humans do it in a more cosy way."
I sort of jumped at the mention of sex before I had got to that bit so I left that part completely out because I just didn't want to have that conversation with dd1 at that time. AIBU to be suprised to find a passage like this in a book for fairly young childrne?