We can't just assign new definitions to encryption. It's encrypted in such a way that a person watching the wire can't see the contents of the message. If you don't want the message on the server, use a secret e2e chat. They are very up front and clear on this matter.

For the vast majority of my messages, I'm fine with them living on their servers. If I need to send credentials to my family, I can use an e2e channel. For me, it's a step up from hangouts and definitely better than whatsapp or facebook messenger.