Gemini 3.5 Flash reversed the singular register recommendation upon learning the plural convention is site-wide across all 38 Arabic pages and matches 5 other languages. Flash affirmed that plural address is 'highly standard, polite, and completely accepted in Arabic for online resources and general audiences' — a full re-sweep is not necessary. This is the Register Architecture Principle validated through expert review: the initial per-page clinical insight (singular is warmer) correctly identified a local optimum, but the site-wide architectural constraint (514 instances, 5-language consistency) made the global optimum the plural convention. The decision demonstrates mature linguistic governance: expert review identifies potential improvements, architectural context determines which improvements warrant implementation. Flash declared the Arabic rollout 'extremely high quality and ready to go.'