IMO, experience indicates that the best code quality comes well away from deadlines. Code written just before a tight deadline or during the recovery period afterward could always use extra scrutiny.

Is it really a surprise that the distractions, disruptions, and fatigue of stress affect a task that requires significant focus, concentration, and creativity? Or that not having much time to review and revise your work will result in lower quality than if you did have the chance to improve it?

Kind of strikes me as a "Breaking news - water is wet!" announcement.