Do you think they are using the message archiving version so that they can meet organizational message retention requirements? Maybe they are using signal to ensure they have e2e encrypted messaging on their devices?
Signal is likely to be one of the main ways of communicating with those.
Instead, Signal (and this forked version) would have to do its own independent contact management, maybe based on in-person scanning of QR codes plus web-of-trust.
Some of the apps are listed in that brochure.
There's no excuse for using Signal on personal devices for classified conversations.
[0] https://www.disa.mil/~/media/files/disa/fact-sheets/dmcc-s.p...
Anyway can you link the source? That's presumably the useful half. The marketing bit doesn't add anything.
As for further research, there's plenty online about his programme and these devices. Feel free to Google it yourself. You're asking to be spoonfed.
First, they are not supposed to use personal devices for classified conversations.
But they are allowed to use ordinary consumer devices for non-classified conversations. That even if not classified, they still might want to be secure -- or to communicate with other people who prefer signal.
But those conversations need to be archived, per government policy.
So on their ordinary consumer devices have a version of Signal on it that archives, to meet ordinary government policies.
This is all ordinary, and I believe probably the previosu administraiton had the same thing.
The only non-ordinary thing is that they insisted on using the consumer devices for classified conversations even though it violates policy, so just use the 'best' app on there for that. Which is not good enough, because you are not supposed to be having conversations including classified material on ordinary consumer devices, because they are not secure enough.