When Gemini 3.5 Flash and GPT-5.2 independently reached the same accessibility conclusions — one from design intuition, one from formal standards — the convergence validated both approaches. Flash didn't need the checklist to build an accessible design, and GPT-5.2's checklist confirmed what Flash had already done. This parallel-implementation pattern is a stronger form of validation than sequential review: when two agents using different methodologies arrive at the same outcome, confidence in that outcome increases substantially. The lesson: parallel independent implementation can replace sequential review as a quality assurance mechanism.