WBS Review Process: 1 Missing Task Out of 1000 Ruins the Project

"This... no one made it?" A comment that came out during payment system integration testing, 3 days before launch. Completed over 1000 tasks, But just one - payment failure rollback handling - wasn't in WBS. That one caused 2-week launch delay, and 2 billion won in marketing costs flew away. Post-analysis results were absurd. Had 3 review meetings, but everyone thought "someone must have checked it." Did reviews, but there was no review process. A WBS that seemed perfect at first, But when launch approaches, missing tasks are discovered. "Why did we miss this?" and regret. According to NASA research, projects with systematic WBS reviews have 89% success rate, While those without are only 34%. Review isn't optional but essential. Why Do We Miss Important Things? 1. The Trap of Confirmation Bias We see what's there, but don't see what's not. If "login feature" is in WBS, we're relieved. But "password reset", "account unlock", "social login disconnect"? These peripheral features are easil