The scenario has a clear methodological limit: Britain may select another design already available in 1920, but it does not receive technology from the 1930s. The 15-inch/50 and 16-inch/45 were contemporary development choices, while a later 15-inch/45 depended on roughly another fifteen years of metallurgical work. The later gun might offer better barrel life and lower weight, but using it here would turn a decision counterfactual into a technology transplant. That boundary keeps the comparison focused on the consequences of choosing F3 rather than on an ideal ship designed with hindsight.
Notable Point · 1:10:02-1:12:27
The counterfactual stays inside 1920 technology
Choosing the 15-inch/50 instead of the 16-inch/45 changes a historical decision without importing a later 1930s gun.