War is a crime. To pick out a single little part of war and declare it more of a crime is silly.
Unfortunately, war is sometimes necessary. That doesn’t mean it’s not a crime, it just means the lesser crimes that are part of war are necessary also.
My other point is that winners write the history books and hold the show trials. If Hitler had won (unlikely, but NOT impossible), Churchill and FDR would have stood in the dock answering charges. They would have been found guilty and hung. Victors justice. Just ask Saddam.
AFAIK, the Allies violated the GCIII as many times in as many ways as the Axis did.

“War is cruelty. There’s no use trying to reform it, the crueler it is the
sooner it will be over.”
-William Tecumseh Sherman
From someone who would know.
There are still those today who think killing a few hundred thousand Japs with atomic bombs was worse then starving to death 10 or 12 million of them.