On pacing:
My own view is that pacing - as in, managing the introduction of new fiction that changes or develops a situation, so that the players are called to make new action declarations in response - is an important aspect of my role as GM.
Burning Wheel expresses it in this way (Revised p 268; Gold p 551 - the text is the same in both editions):
the GM is in a unique position. He (sic) can see the big picture - what the players are doing, as well as what the opposition is up to and plans to do. His perspective grants the power to hold off on one action, wile another player moves forward so that the two pieces intersect dramatically at the table. More than any other player, the GM controls the flow and pacing of the game. He has the power to begin and end scenes, to present challenges and instigate conflicts.
In the GMing advice found in the Adventure Burner and reproduced in the Codex, there is more detailed discussion of shifting focus across different characters (and hence players) when they are engaged in different but simultaneous conflicts.
Upthread I posted about my own exercise of situational authority in my Classic Traveller game, when the PCs were exploring the Annic Nova and being attacked by Aliens (TM). I was beginning and ending scenes, and helping ensure the dramatic intersection of the players' declared actions (eg Vincenzo turning up with his fire extinguisher ready to spray the Alien that Xander had killed).
The description of this aspect of the GM's role in 4e D&D is less elaborate than that in BW, but not wildly different (PHB p 8):
The Dungeon Master has several functions in the game. . . . Narrator: The DM sets the pace of the story and
presents the various challenges and encounters the players must overcome.
When I've GMed Cthulhu Dark I've taken advantage of the extremely loose backstory to manage pacing in a further sort of way (ie in addition to ensuring the interweaving of player actions) - as the session is coming to an end, I've narrated consequences and framed scenes in a way that tends to tie things together and bring them to a head, rather than opening up possibilities and introducing new material. I think GMing Apocalypse World may invite similar sorts of decision-making - eg when
announcing future, or offscreen, badness does the GM introduce new threats and new possibilities, or bind more tightly together existing threats and possibilities and trajectories so that they are careening towards explosion? Knowing what sorts of choices to make here, and having a sense of how they will open up or close down various possible trajectories of play, is important for situation-first GMing.
Ron Edwards has a discussion of one aspect of this under the heading "Minor issues within Narrativist play":
The final minor problem is to resolve play-Situations rapidly and without developing them much beyond the initial preparatory circumstances: "over before it begins." This typically occurs when people are so floored by the possibility of actually addressing a Premise through play, that they hare off to do so before some RPG god notices and intervenes to stop them. Usually, this sort of play is a short-lived phase as the group builds trust with one another.
Letting situations develop is important; but so can be a sense of bringing things to a resolution. Some systems do this "automatically", ie through their own working. I've never played it, but I think My Life With Master might be a paradigm example of this - a system which generates its own endgame. Using quite different methods, a 4e D&D combat also generates its own pacing and resolution. (My own view is that this aspect of 4e is a triumph of technical RPG design.)
4e skill challenges are interesting because they do establish pacing and resolution via system means, but they are very demanding to GM because the GM has to narrate consequences which both (i) respect success or failure on individual checks and (ii) generate a trajectory for the overall challenge while (iii) being open to either success or failure as the checks are made and the respective tallies are built up. Whether or not one calls it "pacing", it's certainly a
thing - an aspect of narration that the GM has to be rather deliberate about if the fiction isn't going to fall flat or seem rather strained.
I think the idea of using
force to manage pacing mostly arises from the use of mechanics that were designed without regard to pacing - ie classic D&D dungeon crawling mechanics, which include map-and-key resolution of declared actions and a lot of hidden backstory that the players are trying to learn - to play games where pacing matters. The system doesn't deliver pacing in itself; and the GM doesn't have the overt authority over scene-framing and consequence-narration necessary to manage pacing in a transparent way (eg because the mechanics being used make scene-framing an upshot of PC movement on a pre-authored map, or more generally make scene-framing something subsequent to a particular class of player-authored action declarations); and so the GM has to use covert means that override what the game presents as meaningful player action declarations.