Some sects of Christianity, generally the more fundamentalist ones will do that as spelling out God is disrespectful. (Especially if the document is erased or destroyed). The tradition goes back to medieval Judaism but started to pop up in the US a few decades ago.
Well, it could be that they are cleaning the ATC center, and controllers aren’t available because of that. As former ATC I don’t buy it though... Washington DC. Center is pretty big... it covers Maryland, eastern Pennsylvania, West Virginia, Delaware, New Jersey, Virginia, and North Carolina, so if they were to shut down airspace I’d think it would be a lower traffic area in there then Washington DC... (unless all they have are single sector flunkies as controllers, or they changed things and can’t reconfigure the radar consoles anymore)
Usually these kind of things get mailed out to everyone with a .mil email... I’ve not seen it come across on mine (granted I’m a contractor, but I still usually get these kinda things)