None of those issues make those mechanics dissociative. There's nothing in hit points, with those examples, that suggests dissociation. Really people could survive a fall,
That's why a said "repeatedly"
Survive a poisoning, and survive a galloon of poisoning are different things[quote and maybe even survive being swallowed (in no small part because lots of critters that swallow whole in the real world don't do a lot of chewing). [/quote] The chewing part is the dissociative one.
Or when a 15 ton dragon LANDS on you, pinning you under it's crushing weight (and doing crushing damage)
From the player point of view, those events cause injury - as they do from the PC's point of view.
The dissociative part is that, after being crushed by a 15 ton dragon, then chewed, then hit by a fire breath with no saving throw (because of being chewed), he can dance just fine.
Or when he falls 200 feet, and after hitting the floor, he just stand up, shake off the dust, and is ready to beat the long jump record while on his plate armor.
I think you're hanging up on the fact that hit points are abstract and, thanks to random variations, the results of these events can vary significantly and may not be particularly severe compared to our real world understanding (where life and limb and injury is decidedly less abstract). But that's not really dissociated.
That a regular, mortal human can be chewed by a jaw that is twice the size and strength of a tyrannosaurus, the spit from 1000 feet against a hard stone floor, just to stand up and sprint just fine because he has 1hp left,
IS dissociative. Your character can't explain why he survived, let alone why he survived without any injury, scar, or broken bone that impede him to run and jump and fight just like if he were unscratched. Or why he can drink a galloon of poison before swiming in a 50m swimming pool of
lava to celebrate that he didn't died in the first volley of crossbow bolts from the fire squad.
If you don't see so, it's because your brain has chosen to ignore the gorilla in the room. Which is absolutelly fine, But the gorilla is there, anyways.