Hussar
Legend
The damage types existed in 1e and 2e.
I don't have access to my 1e PHB so I can't say one way or the other if it specifically makes any mention of damage types. I wouldn't be surprised if the weapon vs. armor table was taking damage type vs armor via the bonus and penalties to hit.
However, different damage types mentioned with different effects do appear in the Monster Manual skeleton entry:
Skeletons "suffer only one-half damage from sharp and/or edged weapons (such as spears, dagers,swords). Blunt weapons such as clubs, maces, flails, etc. score normal damage)".
For 2e: Weapons are listed with a Damage Type (or multiple types) in the PHB" B=Blunt, P=Piercing, and/or S=Slashing. The damage type could alter a weapon's effectiveness against different armor types if using the optional weapon type vs. optional type.
Despite the optional effectiveness vs. armor, the damage type again has varied effectiveness against some monsters. From the 2e Skeleton entry:
"The fact that they are mostly empty means that edged or piercing weapons (like swords, daggers, and spears) inflict only half damage when employed against skeletons. Blunt weapons, with larger heads designed to break and crush bones, cause normal damage against skeletons."
So even if people ignored the weapon vs. armor table in 1e and the optional weapon type vs armor rule from 2e, certain monsters were affected differently by different weapon damage types in the 20 years before 3e.
So, yup, rock paper scissors vs damage reduction. Note, oozes also had differing effects based on what you hit them with.
Damage was never affected by damage type though otherwise.
Note, I'm looking at the 1e PHB right now, and nope, no differentiation by weapon type. And it was an optional rule in 2e which had zero affect on damage, which is what we're discussing. At most, it gave you a bonus or penalty to hit. IME, it was a rule that was not used, much like the weapon vs armour table in 1e. But, to be fair, I didn't realise that they added this in in 2e.

But, we were discussing an orc hitting a PC. So, since he's already hit, the modifiers don't matter do they? The orc did 7 points of damage. What damage type was it? You can't actually tell until you name the weapon, but, in any case, makes absolutely no difference mechanically. 7 points of piercing damage has an identical effect as 7 points of bludgeoning damage. They heal at the same rate, they have the same impact on the character, everything is identical. Again, it's rock-scissors-paper. At best, we're talking a pretty thin veneer of simulation on a model that is a black box as soon as initiative is rolled.
Ok, since we're talking about models, explain this. Fighter one takes 30 points of damage in a single hit. Fighter two gets hit 5 times for 6 points each. Why do they heal at exactly the same rate? It's not like the body heals in serial. Shouldn't fighter 2 heal faster?
And, again, I'll ask, why can't both characters have simply lost morale HP? What in your model precludes that? Or entirely "God touched" HP? I mean, if you have a simulation, you should be able to tell me, definitively, that some things didn't happen. A model should exclude some results shouldn't it?