Can you record your conversations (I think you can)? But most importantly, can you use WhatsApp without a cell phone number? It has to be tied to your email address and not a cell phone.
The recorded conversations are gone when you switch devices. They are saved locally and not on the server.
This sort of blew my mind when I discovered it since I often travel with a second phone and realized to my horror that I could not be logged into the same whatsapp from two phones. Is this the promise of a mobile-first app world?
It's the side effect of running a very learn architecture. It also has a side effect of not being able to secretly subpoena your chat history after the fact too. Now with E2E encryption they can't even do that easily.