If they didn’t announce the near-miss to the world, you wouldn’t know about the asteroid in the first place! So what’s the point of even mentioning its presence? There are numerous programs for asteroid surveillance, which tends to rule out conspiracies – somebody will always blab. Some day we might be able to actively intervene to avert an impending collision (like in many sci-fi movies) but even now I think most people, like the Godfather, “insist on hearing bad news right away.”
This object, 50 meters across, will miss us by 15 minutes and pass closer than many of our orbiting satellites.
If it hits land, a lot of people are doomed to be instantly vaporized. But a great number of other people on the fringe of destruction might well be saved by early warning.