I just finished a near-perfect Gentleman run (I killed zero people, and only punched one person (who deserved it)). Further, I also chose story options which lead to a minimum of casualties.
As you can see from the blog post, Conway apparently counts the people who died during the story in his final tally.
The option which leads to the Acknowledged Ludonarrative Dissonance achievement was not presented while writing the blog post.
I've just finished a completely psychopathic run through (almost every mission completed at Brutal or better, though there was one I somehow got non-lethal on), and nothing particularly special was called out in the ending.
The option that unlocks the achievement was available, though I didn't select it. Besides that, it was about the same as any other ending where you have the option to kill both people in the final mission, and choose to kill them.