If a common human can survive it, it dealt less than 4 damage. And unless you're a monk, tavern brawler or some race that adds a bite attack, that's an unarmed attack and only deals 1+Strength damage.
IRL letal damage is rarely immediately lethal, which is a fact not translated well into the game. The fact he went to the ER is a good sign that it very easily could have lead to death for someone without medical aid.
Also by biting the arm instead of say, the neck, is pretty clear it was a declared non-lethal attack
In either case, he'd have fallen unconscious first. If he did, then sure, but otherwise... And it still wouldn't mean it was 1d6+Strength, because you can still roll high on a d4.
Bite a bear and get back to me. That'll be a better metric.
Bringing realism into D&D is silly. For one thing, we're talking about a levelled character, they're necessarily super human. For another, by your bear logic a .22 rifle wouldn't deal damage at all.
This entire post is people trying to debate game mechanics using real world violence. I'm pointing out they're doing it badly.
And yes, PCs are superhuman to a degree. That's why they have much higher ability scores and, in the case of the barbarian, a bonus to damage while raging. And when they do an unarmed attack, it deals 1 + Strength (+2 for Rage). For a commoner, that's 1 or 2 points of damage. For a level 1 barbarian, that's around 6 points. 1d4 + mods doesn't make sense and 1d6 is right out.
I suggested a bear because it has twice as much health as a commoner, so there's more space to measure. A .22 rifle can kill a bear, but it might take a few shots because of a low damage roll. And it's a fuck ton more likely to kill it than just biting it. 1 point of damage isn't a small amount. We just don't want to measure anything smaller.
The standard hp for a regular human, which for the setting is probably in better shape than the office honed bodies of today, to be incapacitated for combat and eventually die is about 4 (depending on edition).
There is maybe one way a trained human could perform a combat biting attack that would render someone unable to fight back, which is a bite to crush the wind pipe, and with all anatomical protection in place, it seems unfeasible even if they would have the jaw strength for it.