The players in my game and myself (as GM) have (for 28 years) assumed that HPs are in no way knowable by characters. They are a metagame marker for heroic staying power. We post-hoc justify ablation and restoration of HP by referencing the current, and recent past, fictional positioning and use the abstract composite of martial skill/luck/morale/fatigue/divine favor/magic with a very tiny smidgeon of superficial meat (a minor tweak of an ankle/knee/wrist, perhaps a few mm deep laceration, insignificant shrapnel/fragmentation, a bruise, or a topical burn whose only relevance is pain). The last HPs lost before unconsciousness are rarely, if ever, narrated as potentially terminal as well (only if clearly and presently the case...or if definitively so; as in death). If I want to put a lasting injury on a player's character in my 4e game, I'll leverage the condition/disease track rather than using HPs.
This usage doesn't affect our sense of versimilitude. I'm certain the antithesis would.