WhatsApp adds option to use the same account on multiple phones
theverge.com
theverge.com
Shared mailboxes (not mail addresses, but mailboxes) were a common and useful thing which couldn't be done properly in Exchange up to ~2016 and there are still some quirks.
Telegram does have a 1st class desktop client and allows using a single account on multiple phones. It just works and don't use the phone as a gateway.
Also it makes me wonder if this feature could be used to migrate between iOS/Android without losing history. I don't need it, but other people - do.
WhatsApp doesn’t keep your messages and while they are on their servers, they are encrypted with a key only you have.
Security vs. Convenience
Yes, when I share one account with 3 other people I surely worry about encryption.
But anyway, existence of this new (for WA) option confirms what there is a way to solve that problem.
But with Telegram, if you prove to the servers satisfaction that you control the associated phone number, the server will give you the key and all the old messages. So clearly the server has the key and the messages, and also Telegram documents that it works like this.
There is no way to know anything.