FWIW:
I used to be a neighbor of a gentleman in his 70s who was a survivor of Iwo Jima. According to him, the Japanese at that time were ready to surrender, but whoever was the President (I'm hazy whether FDR was already gone or not), refused to accept their surrender. The game plan was, that the Soviets had to get in the War on the side of the Allies, and this had not yet happened. This veteran was quite an intelligent and politically aware individual. and I saw/see no difficulty in taking what he said as fact.
It is true that when I was talking about this matter to another veteran, of similar age, who was a survivor of Normandy, there was no way he would give it credence. But then, he would not give any credence to the reality of FDR's foreknowledge of the Pearl Harbor attack, either. Would have profoundly upset him to believe our leaders would do such a thing to their own people. What a babe in the woods!