Why technical exchanges still missed British armor

How did the United States miss British water-based armor despite constructor exchanges?

American designers did not ask whether Britain had solved a concept they had already judged impractical, illustrating the limits of informal technical exchange without focused intelligence requirements.

American designers had considered related armor ideas and dismissed them, so they did not ask whether Britain had made the concept work. Informal access to British yards and constructors could reveal an answer only when someone recognized the problem and requested the information. The same limitation applied to aerial torpedoes and all-forward gun layouts, where each navy pursued assumptions the other did not examine closely. The missed armor system therefore illustrates both the selectivity of technical exchange and the absence of focused intelligence requirements between friendly powers.