Meta controls the proprietary Whatsapp client software that decrypts your messages and they can have that decrypt and scan the messages for them and send back m

Meta controls the proprietary Whatsapp client software that decrypts your messages and they can have that decrypt and scan the messages for them and send back metrics and how often different words are used. They can of course also have their app de-crypt and re-encrypt the messages to the key of a requesting third party like police or hired reviewers if certain keywords are used. Authorities could also have Google or Apple ship a signed tampered Whatsapp binary to any user or group of users, like protestors, that uses a custom seeded random number generator so they can predict all encryption keys generated and no one else, including Meta, will know. The variant of end to end encryption where third parties control the proprietary software on both ends, is called marketing.