Damage in D&D has always been sort of binary. You either take a grave wound that leaves you bleeding out, or nothing much happened to you at all (except perhaps for a cosmetic gash here or there).
In a game like Rolemaster you can get hamstrung, have a cracked patella, get a punctured lung, whatever. All of these injuries that haven't killed you immediately but are making your life miserable. That's not the way it has ever been in D&D. Even in 3E which had conditions like "Exhausted"... apparently you weren't Exhausted from being stabbed in the lung. Which I would think would be rather exhausting, especially if the guy who did it is 10 feet tall and can juggle oxen.
In D&D a hit either kills/mortally wounds you, or something happens that has no other game effect besides just depleting your hit points. Thus a non-killing blow could be a flesh wound of some kind, or it could be a near miss or a strike that "knocked the wind out of you" to some extent.
Likewise, since D&D has always had 1 hp dudes walking around (and not dying from proud carpet tacks), it must be possible to suffer physical injury that doesn't amount to 1 hp of damage. So a "miss" could constitute a clean miss, or it could constitute a hit that was not life-threatening in any way.
Since 1 hp of damage is enough damage to kill a grown man, we should assume that anything that does 1 hp of damage is a potentially lethal blow. So in general I'd rule that hit points "spend down" the severity of a potentially lethal blow to something either cosmetic and non-lethal, or even something that takes the form of a near miss.
The thoroughly abstract nature of the mechanic means that in the game world, if you were looking through the eyes of a character, you'd see some Misses that miss and some Misses that hit but don't do anything more than a cosmetic injury. Likewise, you'd see some Hits that hit and do a cosmetic injury, and some Hits that miss... you'd see a mortal blow when somebody gets hit by a Hit and taken below 1 hp.