I don't think it follows that they selected the archiving messenger because they wanted disappearing messages. The whole disappearing messages thing was just internet speculation.
> Waltz set some of the messages in the Signal group to disappear after one week
https://www.theatlantic.com/politics/archive/2025/03/trump-a...
https://www.nytimes.com/2025/04/15/us/politics/cia-director-...
It’s also possible that they are using this app to archive chats that other parties _believe_ to be disappeared.
In other words, set your chats to disappear in 5 minutes and convince your target to dish some sensitive info. They think it’s off the record, but it’s instantly archived
The only interesting use case of disappearing messages is that messages one receives will disappear securely, even if they forget about receiving such messages, or have no access to the device at the time.