Yamato's size was politically potent even before asking how it would fare against particular foreign battleships. A public image of Japanese super-battleships might have made American politicians question the risk of leaving older ships exposed at Pearl Harbor. Roosevelt could have faced pressure to return the fleet to San Diego until the Iowa or Montana classes were available. Secrecy prevented that effect because a deterrent must be visible enough for the other side to factor it into decisions.
Notable Point · 50:20-55:30
Yamato and the missed deterrent message
The Yamato class could have had political deterrent value if its scale had been public, rather than concealed.