A reasonable requirement? This is an example of you being wildly unfair to the US and holding them to a standard to which you'd never hold our enemies. Japan can bomb Pearl Harbor and do things in East Asia that would have made the worst Nazis uncomfortable, but you'll call us out for being unfair in the timing of our surrender demands, as if we owed them something. It was a war. We didn't owe them ****. We didn't have to warn them about the bomb. We didn't have to even give them a chance to surrender. Doing so was an act of mercy that they rejected.
The invasion (Operation Downfall) was already planned and ready to go. Nimitz and MacArthur were planning and ready to do it. It was the next logical step. The speculation that they were going to surrender is a classic "if my grandmother had balls, she'd be my grandfather" scenario. Maybe they would have, maybe they wouldn't have. But the point is that when given multiples chances, they didn't. They chose total destruction over unconditional surrender.
Operation Downfall had a dead and missing estimate of 267,000 for our side that extended all of the way to 1947.
1947, folks.