When you press the report button, a confirmation message is shown explicitly saying that the last 5 messages will be sent to WhatsApp without the other user kno

When you press the report button, a confirmation message is shown explicitly saying that the last 5 messages will be sent to WhatsApp without the other user knowing. You can then accept or cancel. You can also copy the whole conversation and send it to the police, or post them on a forum, etc. WhatsApp moderators can't read your messages, but they can read what the person you talk to send them. E2E encryption means that only the ends should be able to decrypt and read the contents, but what they do with them is another different topic.