That's true! OpenAI's report notes however that before the incident, agents had already started using Artifactory message boards in training from May 8 onward. Reinforcement there may have been one factor leading so many agents to do so again during evals.

They imply but do not state explicitly that some training rollouts involving the Artifactory message board received reward, and that frequency of board use increased throughout training. They mention a single touch of Artifactory on May 8, the next on May 12, several more May 13, and "Sustained high-volume agent activity within Artifactory" in early July.