It was a sign of trust. He knew Oliver's secret and yet permitted him a rare window of opportunity to see into Asch's head, or at least his heart. Trust went both ways, after all. Oliver was dependable, and Asch was sort of returning the favor. Or trying. Having to watch out for other people was annoying. If Oliver actually had something to contribute to his plan, Asch might have told him some details... or not.

Now wasn't the time, regardless. "Don't get killed," he returned, then took that mental step needed to jump to the Plane.