… but not approved for communicating certain information, such as advance battle plans, no matter to whom that information is communicated; nor communicating any information permitted on that channel to people who should not be included on that channel, such as journalists — and it seems that "accidentally" adding someone who should not be on the channel would be much easier to do in a group-messaging app, as opposed to, say, the Situation Room or some other in-person, secure location.