The what’s app is encrypted to get to your phone so transmission is protected, however to view your message it is unencrypted (obvious) and at that stage WhatsApp will parse it for key stuff such as Child Sexual stuff, or other threats they have determined they look for, that then triggers a data send back to the mother ship. The problem with this is if the Government wants to silence a political opponent or journalist they can go to Meta and request a search other than CSAM. So end to end encryption via any META product is a joke