Its another gimmick feature that serves no purpose.
Do you really think Larian will bother to implement alternative consequences for nearly every fight based on you having killed or just K.Oed them?
I mean, at this point anything is possible. They certainly don't skim on reactivity.
And not every fight. For example, I took no issues with robbers having no special interaction, as they don't appear later in the game anyway. But for example, if Laez has a further chain of events if you not recruit her, she could still include her, if you left her unconcious. And definitely NPCs should recognise knocked down NPCs as killed. Gothic1&2 managed to find a way to have non-lethal engagements, I am sure Larian can do even better job.