It seemed like some of the centers were torched before they became operational.
Thats probably what they meant. There’s no way, in the era of social media, to keep a center secret once it goes into operation.
But at that point it also becomes much harder to attack. Not just physically (because of all the people there to stop such an attack, but psychological as well since the arsonist is moving from arson to attempted murder. And to murder if someone gets killed.
gotcha.