Once "knocked out" if you hit enemies again with blunt or non-lethal weapons they usually kill. This means that if an enemy is down, you can go back and kill them, or by accident kill them on a double swing or shot. Makes it hard to NOT kill if that is your desire.
IT does allow you to get extra XP by knocking them out, then going back and shooting them, as example use the cyber hack poison to knock most enemies down, then use a pistol to get more XP by executing those knocked out. IT also allows you to easily get the achievement on the skill to jump down on 3 enemies and kill them with the cyberware...knock 3 enemies out, pile the bodies up and then jump down and activate the power landing and poof 3 dead and achievement.