To me the shocking thing about the USA Gov't is that they manage to lose trillions in the defense dept that they can't account for, but somehow are unable to develop their own communications apps? What? Signing messages with a crypto key takes like 4 lines of code. It's not rocket science. Yet they use some corporate app?
My only theory is that they're pretending to have only 'Signal' so that when they want to they can allow hackers to "see" stuff they WANT to be seen. Like a disinformation honey pot designed to misdirect America's enemies. While they actually have a totally separate secret app that is secure and is developed by the NSA.