The paragraph is correct but misses the point. Whatsapp will re-transmit messages with a key provided by whatsapp without ever giving the user the option to ve

The paragraph is correct but misses the point. Whatsapp will re-transmit messages with a key provided by whatsapp without ever giving the user the option to verify that key. Even with the opt-in, the message will be re-transmitted. All the opt-in ensures is that you are notified of the key change (a notification you receive after the message has already been re-transmitted under the new key)