Yes, it is different, and that's quite interesting. My NPCs are more like characters in a play - they tend to write themselves - and I find that entertaining in itself. Maybe that's why I dislike the idea that they might be arbitrarily cut down by dictat - to me, they are "people" with a right to existence. I can quite see, though, that your way of using them is equally valid from a game point of view.
For "people with a right to exist", you sure went from "DM hand waves the death of a single nameless guard for expediency" to "PC's are implementing wholesale slaughter and the guards are helpless to resist" awful fast.
You removed the control from the DM and put it in the players hands, and then expanded it from a single guard to a whole regiment of guards (from where?), all in a single leap of logic with no explanation. No one except you was suggesting mass slaughter of a regiment of guards in a single minute. Turning an off-hand suggestion into Auschwitz seems a bit extreme to me.

So while it might be a topic best suited for another thread, I don't think anything useful would come from it.