Other ways of understanding the "zero defects" concept are the phrases "practiced infantryman's eye" and "attention to detail."

The focus on these "details" happens to come about, I think, because resources may not be available to assess whether a unit is able to accomplish its mission. As a result, indicators are used instead. This line of reasoning is based on the fallacious presumption that your attention to detail, like keeping that "autobahn" in the barracks at the 7th Army NCO Academy spit shined, indicates that you will be able to get the big things right too.
Even if the extrapolation from detail to big picture achievement is correct, the big picture may vary as well. The meaning of mission accomplishment changes depending on time and place. What indicators one uses will probably change as a result.

Leaders accustomed to peacetime will use different indicators than leaders used to combat.
--It's pretty unlikely that a soldier will get blown up by an IED on Fort Bragg's Sicily Drop Zone, but that soldier may well have a parachute malfunction during a practice drop.
--A units' billets on Fort Benning will probably not be overrun by the irate citizens of Columbus, but add a little alcohol and some of those citizens may get in a fight with a group of troops at a Redsticks game.
--A Fobbit SGM may look at whether/how you wear your reflective belt; a PSG in a COP perimeter is more likely to look at whether/how you put out your aiming stakes for the machine gun. But at some level they both are trying to "conserve the fighting force" AKA keep troops safe (I hope).

Good leadership entails being able to distinguish what kinds of things "count" when assessing what really matters and applying that based on when and where one is.