Aren't you handwaving the healing spent?
But, in any case, you are right. I do have a big chip on my shoulder on this. And it tends to come out and I appologise for that. It's just that the argument, "If you do this, then you invalidate my play style" means that your play style becomes prioritized over mine. Because, honestly, I don't have any problems with any of these things. But, we can't add any of these things because your insistence that adding these things invalidates the way you want to play. Even if the additions are 100% optional. You've closed off an entire design space simply because of how you interpret HP.
And it's an interpretation that doesn't really carry a whole lot of water in 5e. Not when HP return after a long rest and we have Hit Dice and things like a Fighter's Second Wind. We have non-magical healing in the game that make absolutely no real sense in the game fiction. My fighter can take 10 damage, Second wind, short rest and repeat infinitely so long as I keep rolling higher than my damage on my second wind. What happens in the game fiction? Who knows? There's no way to narrate that.
And before anyone says that Hit Dice represent meat, I would ask, why can't they be healed? I can use the most powerful healing spells in the game, Heal or whatnot, and not a single Hit Die is EVER replaced. The only thing that recovers Hit Dice is time. Two days at most, but, it will not replenish any other way. So, it's not actually wounds that are being recovered, because then healing magic would work. It's 100% plot armor.
The whole HP=Meat line just makes so many inconsistencies in the narrative of the game. Trying to directly apply HP to the in game fiction doesn't work. Not beyond anything other than the most casual of examinations.
But, despite that, we are not allowed to have certain mechanics?

Why not?
Like I said, you lost this argument the second 5e hit the shelves. You really did. There are far too many inconsistencies in the idea of HP=Meat for it to actually work without a LOT of blinders being applied. OTOH, if you follow what's said in the PHB and presume that HP are whatever is needed at the time, you open up all sorts of design spaces that people can choose to use if they wish, or ignore if they wish.