@Fanaelialae
That quote from the 1st edition PHB was really helpful. I've never read that book and I doubt I'll ever have the chance, so thanks for including that.
I think it comes down to a fundamental difference in perception that I have from many others when it coms to what HP represent. An analogy: some people say that money is a measure of a person's success in life. Others say money is a catalyst for confict, or the root of all evil. I see $$$ as nothing deeper than it's physical implications: it is a way to purchase goods and service. Nothing more. Everything else is existential to that. Kind of like how I see HP. Hit points are physical damage.
Luck, fortune, will to survive/persevere....all addressed by other things.
But I see where others are coming from.
In some games, hit points are definitely more physical. Typically, these games let the hit points increase only very slowly - or not at all. Instead, the typical defense against injuries are defensive abilities like dodges and parries or relying on armor. Some games also add an extra "buffer", like action points, conviction, hero points, karma, possibilities.
I would probably characterize this as a "wound (point)" system.
Each hit that deals damage really causes wounds. Your goal is to avoid getting these hits, you don't want to be wounded because it will kill you quickly. The in-game resources like action points or conviction fulfill the same purpose as D&D like hit points.
(Let's call the varied action points & co systems simply action point systems.)
In a "real" or "D&D-like" hit point system, you expect to be hit. Sure, you prefer avoiding it, but you expect it, you just don't want to be hit too often. Because that leads to [-]wounds[/-] death.
In both models, you have a specific resource that you don't want to go out, but it is implemented differently.
The wound point system with the action point resource system is in a way less abstract. The wounds are really damage, you don't have to decide whether it was luck or pain tolerance or a real injury the character sustained. Without the action point system, the game as a whole describes what "really" happens. Someone swings a sword at you, your left arm is cut and broken. The action point system allows you to change this story, from "arm is cut and broken" to "narrowly evades the blow".
Of course, there is a cost to this - you have to track extra values, not just the hit (or now "meat") points, but also the action points.