They wouldn't even be able to.

WA is end-to-end encrypted.

WhatsApp is closed source. They could backdoor it if they wanted to (or were forced to).

And so in Apple and iOS. What is your point?

His point was that it is technically possible for WhatsApp to add a backdoor. Apple could too.

sure, but

a) that would involve changing the code base b) more privacy minded users would just delete the messages or not update.

With almost everyones backups stored in plain-text, making it all a little silly.

Think about it for a second: you can re-establish your WA account on a new device using only the SIM card from your old device. SIM cards don't have a storage area for random applications' encryption keys, and even if they did, a SIM card cannot count as "end-to-end" anymore. Same goes for whatever mobile cloud platform those backups might be stored on. And you'd hope Apple or Google aren't happily sending off your cloud decryption keys to any app that wants them. Though maybe they are?

Reestablishing your WhatsApp account on a new device doesn't give access to your old chat messages, you need to restore a WhatsApp backup for that. The backup doesn't need to be stored in the cloud, you can choose to create a local file and manually transfer that to your new device.

In any case, as soon as you start using WhatsApp on a new device, users in the chats you participate in will receive a message informing them that your encryption keys have changed.

It's all lip service, because the UK Govt wouldn't ask them that. WhatsApp messages are EE2E. They probably already handover all the metadata surrounding those messages.