Vespucci, good stuff.
Rather than introduce the positions myself, let's take a quote from the 4e DMG:
"When you start a campaign, you should have some idea of its end and how the characters will get there. Fundamentally, the story is what the characters do over the course of the campaign.
Keep that point in mind—the story is theirs, not yours... If the characters go in drastically unexpected directions, try to coax them back to the story you want your game to tell without railroading them." (Emphasis mine.)
This is classic incoherent stuff - and it occurs in so many RPG texts that the Forge has a name for it - "the impossible thing before breakfast".
The advice in the same book on running skill challenges points in favour of the bit about the story being the players'. The advice in the same book on scenario design points in favour of the game being a GM-driven railroad.
I would like to think that WotC could try and clear this up, but they have conflicting interests - between giving coherent guidance to players of their game, and selling scenarios that are primarily about railroading.
Paizo's Gamemastery Guide has the courage of its convictions
This makes sense - Paizo is, after all, in the business of selling adventure paths, ie predetermined stories. (Interestingly, though, I think Pathfinder would more often be labelled old school than is D&D, despite this much less unambiguous guidance to GMs. This is one reason why I think new school/old school is not a very illuminating contrast.)
In his article D&D Campaigns in White Dwarf #1, cover dated June/July 1977, Lew Pulsipher notes two distinct styles within D&D.
<snip>
This distinction, between gamist and story-oriented play, is very much alive today.
Of the story-oriented play that Pulsipher identifes, some is clearly simulationist (the players experiencing the GM's story) while the more gonzo stuff could be either very high concept simulationist, or wacky light-hearted narrativism.
Pulsipher himself clearly like a very heavy simulatonist platform to support his gamism.
The epics formerly were largely expected to be consequences of campaign play: YOUR epic in YOUR world caused by YOUR player-characters.
<snip>
The DM sets up situations rather than preparing stories; "the adventure" is not a pre-game text, but whatever enterprise the players have undertaken.
If I've read you right, you're presenting this as old school.
But it could equally describe the GMing advice in narrativist games like Maelstrom Storytelling, Burning Wheel etc - which, presumably, are new school (or, at least, not old school).
What it
does seem to me to contrast with is railroading play (what the Forge, as you note, calls High Concept Simulationism) of the Dragonlance/Vampire/AD&D 2nd ed variety.
My conclusion (which may be in agreement with you - I'm having trouble following the precise argument of your posts) is that old school/new school on its own is not a very adequate or precise contrast.
Because while modern narrativist games give the same GMing advice as that which I have quoted from you, I
think it's pretty clear that they aimed at producing a different play experience from a lot of classic D&D play.
Iin the old school, the DM had to be upfront that he was running only a limited campaign milieu, because that wasn't the general expectation. In the new school, the DM is encouraged to pretend he is running an open campaign milieu, while in fact running a limited campaign milieu.
IMO, Illusionism--whether manifesting in that bad 4E GM campaign advice, or in running something like the giant series as a tournament module while pretending not to--is not characteristic of any school, old, new or indifferent. Rather, it is a particularly incoherent symptom of cognitive dissonance that can infect any school, when someone wants to have their cake and eat it too.
I think that Crazy Jerome is closer to the truth here - where I'd quibble is with his use of "illusionism" as a euphemism for "lying".
I think illusionism is better used to describe a type of consensual GM-guided play, in which the players - by immersing themselves in the colour of their PCs and the gameworld - wilfully blind themselves to the plot-manipulation in which the GM is engaged. The seeming popularity of so much 2nd ed campaign and adventure material suggests that this approach to play is (bizarrely, to my mind) very popular. The continuing successful publication of adventure paths for D&D is further evidence for the same conclusion.
But I can't accept that all these players are being tricked/lied to. They must
want the GM to direct the story.