And I'm asserting it really can't. As alluded above, by myself and others. The point
@pemerton made about "explanations just past the page," for example. If the standard requires that full-on everything be justified purely within the literal words of the text, an enormous swathe of fiction instantly ceases to be immersive solely because it doesn't go into a lot of unnecessary detail about grain imports and industrial capacities etc. Since you seem to be cool with the Rivendell example, it then behooves you to explain why
those handwaves are acceptable, but game-related ones are not.
The original Alexandrian article makes an explicit discussion of how character creation is "dissociated" but not a problem for being so, because it's not part of at-the-table play. This is critical, since many people (IIRC including yourself? please correct me if I'm wrong) have emphasized how the Alexandrian article is (allegedly) not saying "dissociated = bad"
specifically because this section is present. Given that part of the explanation of the concept very specifically calls out character creation as "dissociated," and AFAIK no one has said otherwise about character creation rules prior to your post here, I had assumed this was part of the package.
This, incidentally, just gives another demonstration of why I think the whole concept is just too much of a problem. Even the people who intend to use it seriously have
major disagreements over what does or doesn't count, and which parts of the original article are relevant or important.
It is quite possible I am mistaken. But my understanding of your argument is as follows: Hit points do not meet the narrowest definition of "dissociated" mechanics, because (per the Alexandrian article where the term was articulated) "dissociated" mechanics are ones that must relate to
choices the character and player make. Players do not make choices about what their hit points are, generally speaking. They may make choices about (say) consumable resources which can restore hit points, but in the way the article uses the term, hit points
themselves are outside the scope.
Yet you have said that they they clearly
are "dissociated" (and I, personally, agree with you). This implies generalizing beyond the narrow limit: permitting us to include choices
informed by mechanics, not merely ones directly
invoked by them. Characters do (presumably) have awareness of their overall state of fitness and ability to act, but they do not and realistically
cannot know many of the things that hit points allow a player to know. I gave the example way upthread of a character (like, say, a level 8 Fighter with 14 Con) deciding whether to jump down a 100' cliff face. If that character has full HP, the player can know--for certain, purely from the mechanics--that falling damage cannot kill the character, as the fall can only do 10d6 damage (1d6 per 10') and the character has 68 HP, indeed the character is very likely to take no more than about 44 damage.
That is the generalization. Going from "this concept
only applies to things that actually
require player choices" to "this concept applies to any mechanics which
inform player choices." But if we make that generalizing step, then everything that arises from character building--based on the original article explicitly calling character building "dissociated"--is necessarily
informed by that character building, and thus necessarily "dissociated" for exactly the same reason that HP are.