Voadam
Legend
Yeah, the 1e DMG is for advanced while most of the intro modules are in the B series for basic. But even B2 is set up for possible faction play with multiple different groups of humanoids. I don't remember a lot of advice in B2 but it seems inherent in the setup. Also B/X has the whole reaction roll thing going on so that hostilities are often possible but not a default always thing RAW. Mostly that was left up to the DM to free form though is my recollection of it.Which is weird and funny considering that Gary went into some detail on it in the 1979 DMG. You'd think that advice would have been incorporated into TSR published designs, as a rule rather than as an exception.
Although perhaps part of the issue is that after about '81 or '82 TSR may have been aware that their primary buying demographic was trending younger and younger. More and more middle school-aged boys, fewer of the college students and adult wargamers who made up most of the market in the '70s. In that context, simple "the monsters attack!" encounters make more sense, for kid gamers to run.
I remember some discussion of factions and responses in the AD&D Temple of Elemental Evil and I certainly ran it that way in the 80s as young teen as the AD&D party I was running moved on from starting in B1 to multiple assaults on the Moathouse and the New Master.
AD&D had a bunch of competition modules that set things up to be fairly linear and static to provide similar challenges to wide varieties of groups running under different DMs at a tournament and allow judging and competitive ranking based on module performance.