Right, that makes sense, although the article doesn’t go into detail about how the server decides when it’s time to delete a message.

It also doesn’t back up your claim that multiple devices sharing the same account will ever exchange messages amongst each other. Which would be a technical nightmare BTW since they could be located behind firewalls etc. and this still require a central server to coordinate. Might as well keep the middle man in that case and leave the messages on the server until they’ve been retrieved.

My initial point therefore is mostly correct: messages ARE stored on their servers in encrypted form for an unknown length of time, although likely not forever.