The most important bits aren't the technical aspects, but rather who controls them.
It is entirely meaningless when the keys are generated by a closed source application, when there exists no way to verify that the data isn't exfiltrated before its encryption or after its decryption, or when the only transportation method is entirely in an untrusted party's hands.
When all those things are controlled by the same entity, especially one with a history of abusive and manipulative behaviour such as the operator of WhatsApp, it's not "encryption" but a "bad joke".
It is entirely meaningless when the keys are generated by a closed source application, when there exists no way to verify that the data isn't exfiltrated before its encryption or after its decryption, or when the only transportation method is entirely in an untrusted party's hands.
When all those things are controlled by the same entity, especially one with a history of abusive and manipulative behaviour such as the operator of WhatsApp, it's not "encryption" but a "bad joke".