As has already been pointed out, this is a complete strawman. Clearing out a safe zone is a tradition that goes back well past 1e.
Wait, what? Since when?
I'll happily grant that not all random encounters are wandering monsters (e.g. landslides, funny sounds, etc), but wandering monsters are indeed a type of random encounter.
But perhaps the problem here is one of definitions; it seems as though you've a nontraditional definition of wandering monsters that isn't the same one that I've been using. From the 1e DMG, pg. 230:
So that patrol of monsters certainly qualifies, and in fact, that very same book includes, in the sample dungeon section on page 94, the following chart:
...for some playstyles. In some campaigns.
In others, "Oops, I just wandered into your path" is just fine, reinforces the verisimilitude of the milieu and is tons of fun.
Not to be repetitive, but just because you like it one way- and the Angry DM prefers a certain style of adventure design- does not make it the "right" way to do it. It may be right for you and the Angry DM, but I 100% full-on no-doubt assure you that it's not right for everyone, because it isn't right for me or my group.
That's fine, but you aren't using it in the traditional and understood way. It's like if I talked about enchanter specialist wizards but called them psions because it's easier than typing out enchanter specialist wizards. It muddies the discussion when we aren't using the same definitions.