This is why I say you don't undertand the 4e combat resolution mechanics. This claim isn't true of 4e; hit points aren't a description of anything. The toughness of a creature is described in the fiction - just as (say) JRRT conveys that the cave troll is tough. The hit points are then a device - together with AC, attack rolls, damage dice etc - that are used to determine the outcomes of fights. That is to say, they are a component of a resolution system. And this is all subsequent to the fiction of how tough the creature/NPC is, not an input into it.Hit points per se aren't a part of the game world but what they describe - a creature's general degree of toughness and resilience - is.