What if Germany mastered modular shipbuilding by 1939?

How would World War II change if Germany made modular warship construction work by 1939?

Germany would gain capacity, but the Allies would probably share the technique and exploit it at greater scale, while German overengineering could erode much of the benefit.

An early German breakthrough is unlikely to remain a monopoly because Britain already used sectional construction in some submarine work. British yards produced sections, including pressure-hull components, and joined them during assembly. If other powers adopted the same advance, their larger industrial capacity could make Germany's position worse. Hull design also affects assembly: an external belt such as the King George V class's is easier to accommodate than an internal belt requiring very precise integration. A tendency towards intricate designs could therefore reduce the benefit of faster construction.