It was a question of the form trying to figure out how you deal with "X", and he denied X having ever happened, despite that being a core part of his current role.

He was an internal candidate, we were interviewing him to see if we could trust him with more responsibility (more X specifically), since the new role shouldn't cover up X when it happens. The role involved doing X for himself AND for other people.

Similar to the form of "tell me about your biggest weakness" and you responding with "I have no weakness".