I think this is meant to detect insider knowledge of imminent risk of a nuclear attack. It's not meant to detect if nukes are already inbound.
In reality, look at things like the 9/11 attacks, the 2004 tsunami, the Covid lockdowns, the Maduro raid: the elites didn't fly out all at once shortly ahead of time before the plebs knew what was going to happen. No doubt you can think of good reasons why it didn't happen in those circumstances, but trying to come up with a scenario where it actually would happen is quite a bit more challenging.