Ruin Explorer
Legend
Twenty damage is enough to KO a warhorse, and sufficient to kill many people outright. A DM is absolutely entitled to make that call, in their attempt to reconcile the mess that the game has made of HP and healing.
No. In D&D damage is not absolute. HP are not "meat points". That's why they grow, and why a high-level Halfing has the same number as a moderately sized red dragon! That's not really a subject for debate. The debate was over in the 1970s, before I was born, probably before you were. This isn't Cyberpunk 2020, or one of any number of other RPGs with relatively absolute damage (a huge amount actually use HP or quasi-HP or soak systems which likewise render damage not absolute). If you want a system with absolute damage, they are out there, and they are not 5E (or any other kind of D&D or close D&D relative).
Further, you continue to fail to address the gigantic problem you create by asserting they are meat points and that damage is absolute, which is that until you hit 0 HP, there are 0 consequences. Again, there are plenty of systems where this isn't true. If this aesthetic/gameplay element of D&D is something you cannot accept, which it appears to be, I would suggest running one of those instead.
The fall problem is also pretty hilarious with the "damage is absolute" thing, given an elephant can walk away from any distance of fall on average, which er, doesn't seem very plausible (less plausible than a human by far, I'd suggest). D&D is simplifying things and using a system that is does not treat PCs as some sort of doner kebab, slowly being carved away at until they keel over.
If there was a consistent solution, and the DM chose to ignore it, then it would be their fault for choosing to do so. As it stands, though, there is no good answer. That interpretation is far from the worst I've seen. At least they're trying to make sense of it.
Again, no, they're actively making an effort to make a mess of it. Claiming someone is "impaled" on a spike, which strongly suggests it's gone in one side of the body/limb and out the other, in a fairly solid way, is going out of your way to mis-portray what has actually happened in most cases.
My example was a 50 HP character taking 20 damage from a spike trap. He's not even "bloodied" in a 4E sense (something 5E doesn't have as a set concept but clearly has a notion of). He's probably winded, battered/bruised, alarmed and has sprains/strains from falling among the spikes, none of which went through him. Maybe some broke on his armour or whatever. But impaled? Is not a legitimate interpretation, and is not "trying to make sense" of anything. It's trying to misinterpret it in order to make HP into meat points. Whereas if he was on 14 HP, and took 20 damage from spikes, I'd say it was legit to say he was impaled (though probably only by one of them if he was still able to make death saves).
It's not that 5E's rules are impossible to improve on, but it's not like vast change is needed. The main issue seems to be the same issue I saw in 2E in 1989 - some people think HP are "meat points".