My interpretation is that he meant it's alarming to see the government suddenly openly suggesting an e2e messenger because it might hint to the agencies having discovered a hole in the Signal protocol.
I highly doubt that personally, but that's what I read from nimbius comment.
So then why would they want the military to use it for internal discussion? If the govt is aware of a hole, then other nations might be aware of the same or a different issue.
It does matter. Soldiers talk about sensitive stuff all the time. You don’t want schedules, personnel, whatever, leaking through inane conversations to people we’re at war with.
Unfortunately, classified comms of various classification levels spill over into publicly available channels all the time, both accidental and out of laziness, but also sometimes an immediate necessity.
I highly doubt that personally, but that's what I read from nimbius comment.