A deterrent built around very large, heavily armed battleships depends on opponents knowing enough about them to fear their power. Concealing their capabilities prevents an enemy from allowing for them in its plans. Waiting until the ships entered service to announce them would be too late to affect a decision for war taken beforehand. On that reasoning, secrecy weakened the deterrent return on Japan's investment in two very large ships.
Notable Point · 35:01-36:12
Yamato secrecy and the limits of deterrence
Secrecy raises a problem for the argument that Japan's largest battleships could deter an opponent through their superior armament.