"the methodical industrial organization of the killing"
I think this is the difference. My mother's older brother was a US Army officer during WW II. He saw combat as a platoon leader in the Third Army. My grandparents were ethnic Germans from Hungary. After the war, my uncle was assigned, apparently because he was bilingual, to a US Army team investigating the death camps. He had always been proud of his German heritage, a heritage of music, science, and philosophy. He couldn't reconcile that with the cold engineering of mass murder that he saw. My aunt said he would awake screaming and crying decades afterward, not because of his combat experiences, but because of the camps.
Last year at my high school reunion a classmate told me of visiting Armenia the prior year and seeing the barn where her grandmother had been burned alive with eighty other women. My once cheerful classmate started crying as she told us.
I saw a PBS special about the Wannsee conference and the cold engineering of mass murder. The scale and terrifying coldness of that makes the Armenian genocide pale in contrast, although I do not make light of that.
I can understand hot blood, Lord knows, I have been in a killing rage myself. But, like my uncle, I cannot understand cold blooded mass murder of strangers.