Originally D&D hit points
were the ability to take damage. "Cure", "heal", "rest" were all based on that concept. I don't remember if it was explicit (the original books were just pamphlets and lacked extensive discourses on concepts and design philosophy), but it was pretty obvious. However, from the start, D&D took a lot of flack from the ridiculous results, like competent characters easily being able to survive being squashed by a large boulder. The patch for this was to reinterpret "hit points" as an abstraction reflcting the ability to survive by any means, not just to able to take the damage. This was made "official" in AD&D in 1980 although many (including me) had already come up with it on their own. I remember this pretty well as I'd had numerous arguments with people over reinterpreting hit points and really enjoyed shoving that passage under their noses when it came out.
Unfortunately "cure" spells and the like were never reinterpreted in light of the reinterpretation. In fairness, D&D is a game, not a sim, and the HP abstraction works pretty well for having fun regardless of the bizarrities simulating certain events.