In 0D&D - as in every ed but 3.x (though even 3.5 had inferior 'NPC classes') - PCs and monsters were statted out quite differently. And, in the classic game (though maybe not so much in 2e, IIRC), 'monster' could include any foe the players met, including other people. 'Men' was a listing in the MM. Even when an NPC was nominally of a class, it would get a condensed set of stats that might (or might not) jibe with an actual full PC write-up of the same class.
But we know from examining the source material that OD&D HAD a stance. Its possible it was a largely happenstance, but it was a stance of some sort! The level names of PCs makes that clear, the fact that PCs were drawn from the exceptional singular figure rules of Chainmail, and the mere fact that they could advance whereas it was explicit that most NPCs didn't ever advance. While its possible to say that NPCs and PCs use the same rules (henchmen are built using PC rules for instance, as presumably are many hostile NPCs though it isn't really stated) PCs are consciously designed to promote the game's agenda, not 'just like NPCs'.
I don't know OD&D as well as I know AD&D, and my grasp of Chainmail is weaker again.
In 1st ed AD&D, as I noted in my post, all this is definitely the case. Looking at OD&D, 1st level fighters had 1D+1 for hit dice, whereas the "men" in Monsters & Treasure have 1D - so the PC is stronger. On the attack side, a 1st level fighter is "Man +1" which is better than a typical NPC. In the aternative combat system, though, there is no 0-level column like there is in AD&D (and in B/X, labelled "Normal Man" rather than 0-level).
I agree that PCs were built in a way to promote the game's agenda. I still feel that the issue of "dramatic weight", as part of agenda, hadn't been given the same attention in this early D&D design as a contemporary designer would give it.
I'd say it was games like RuneQuest that consciously decided to use the same stats to describe both PCs and monsters/NPCs
Yes. I'm not saying that OD&D used the same stats for PCs and NPCs/monsters. I'm saying that I don't think the element of "dramatic/literary" weight had been given the attention that a modern designer would give it.
Even in the case of RQ, I don't think the design was same stats in order to deliberately push an agenda of "no dramatic weight for PCs" - to the extent that that was a consequence, it was more of an unintended consequence, I would say. I think the motivation for the design was a view about "elegance" or "simplicity" of design.
I'd note, also, that 4e uses the same mechanical format for PCs and monsters/NPCs. It's just that the methods of generating those stats, and the details of them, give PCs a heft that monsters/NPCs lack. So I think the issue of "same stats" and the issue of dramatic weight, while not unconnected, aren't identical either.
Back in the day, designers may have not even thought about it, and ended up drama-neutral as a default. There was no choice or agenda, because it never occurred to them that they should think about it.
I think this is probably true of the very earliest D&D (by the time of AD&D, I think that design awareness was growing). But it is also somewhat orthogonal to your claim upthread.
Even if a designer builds a "drama-neutral" game by default, that doesn't mean that the
game lacks an agenda, in the sense of a default playstyle towards which it will push participants. Upthread, you said "It's like the game is forcing its own agenda on you". Well, a "drama-neutral" game will have that effect too, whether or not the designer set out to achieve that effect, or noticed it in play him-/herself.