Or by announcing it, they give the impression that it is something they have not done previously. Indeed, they might want to see how some people react to this and a sudden stream of deletions of social media posts by individuals/groups after finding out about this - would be of interest too them.

Another possibility is that the military like a large company has many arms and legs and highly possible that it is something that is already done, but by some seperate part of that collective that the rest are not aware of. I've seen a company the size of 100 have two people do the same project for nearly 6 months before they realised about the other and the duplication of work. More people, more separate divisions/locations, more chance duplication on some levels happens.

For me, I suspect the later, but equally mindful that as a tactic - doing something and then after you have done it, say your going to do it to gauge reactions - is a tactic that would not be out of place in any military intelligence collective.