Keeping with Anne Frank's diary's light sexual content, I'd say it's healthy for a child's development to read about experiences of similarly aged individuals.Yes, and they're also developed enough to handle profanity or maybe a punch in the face. Can they handle something is the wrong question. Should they have to is the question.
It can provide context for thoughts or feelings they might be having themselves, it tells them that they aren't the only ones with certain feelings or thoughts and that they aren't weird for having them.
And for children who don't share those thoughts or feelings, it shows them how other people might have different thoughts and feelings than their own.