On a personal note, my father served in WWII and then again in Korea. When the troops were assembling to go to Korea, my dad was in position to see the plans for the invasion of Japan. Those plans were detailed to the unit level and included a casualty estimate by unit. His WWII unit was slated for the second amphibious wave of the initial invasion of Honshu, and was estimated to have 90% casualties. There was also no desire in the US to prolong the conflict through blockades or other diplomatic means after 4 years of fighting.
Needless to say I'm biased towards the option that was taken, since the odds are against my existence had the invasion been used as planned.
I wonder what was your dad's rank and clearance if he, despite being slated to take a place in the landings, was able to see it. Not something the brass would want the soldiers to know I think.
He saw it as an officer getting ready to go to Korea, not as a soldier in WWII. The base used for logistics in the US in 1950 still had those plans on file though they were obsolete. I suspect that their clearance had been reduced accordingly.