Sorry about the delay, I've been traveling.
The principal significance of a player move in a RPG is to establish some element of, or contribution to, a shared fiction.
So when
@chaochou says that player agency depends upon the following:
*Transparent goals for characters - often through authorship of them by the players
*Facilitation of that authorship through group creation of setting and/or situation such that character goals are given meaning and context by player choice, not secret GM backstory
I do not see any problematic "conflation".
If the situation is created solely by the GM - which is to say, if
@chaochou's final dot point is not exemplified in play - then when a player declares an action they don't know what is
really at stake in its resolution. Because that will flow from the GM's decision-making alone ("secret GM backstory"). Which means that the relationship between (i) the player's decision as to what their PC tries to achieve, by performing this action, and (ii) what happens next, is not under the player's control. It is being decided entirely by the GM. Hence low player agency.
Why should stakes be set at the level of an action declaration? The game is in stringing together a series of actions that will produce the outcome you want, and the whole creative expression of play, the thing I'm calling "ludic agency" comes in having different possible sets to pick from. Any game that can be resolved in one action is necessarily going to be very low-agency, unless you're playing on a repeat loop and moving the actual goal to something else. Rock-Paper-Scissors is an almost no agency game (you can make a choice, but the choice is meaningless) but it has the potential if iterated between two players repeatedly to be slightly higher agency as you start getting into patterns, strategies or at least yomi.
Conversely, the way a scenario "yields to" player authorship, in a RPG of the sort chaochou has in mind, is because the players are able to declare actions for their PCs that, if successful, result in the fiction changing in ways that give affect to the players' visions and aspirations for their PCs in the situation. The RPGs he has in mind are exemplified by Apocalypse World and Burning Wheel. And the way these RPGs secure that connection between declared action and result if the action is successful is by giving the players input - whether direct or indirect - into setting and/or situation.
This is the precise differentiation I'm talking about. Ludic agency is your ability to affect success/failure by adopting different strategies. In order for it to exist more than one strategy must potentially yield success (the situation should be a board state, not a puzzle), and strategies must be able to be evaluated; some must be more likely to succeed (or to produce different, more desirable board states for future strategies to be tried) than others.
You're describing narrative agency here, in that the player has control over narrative outcome in some circumstances. Some narrative agency is intrinsic to TTRPGs in that players can generally set their own victory conditions, a thing that is rarely true in other forms of gaming outside of maybe some simulation focused wargames or open-world immersive sim video games. You're arguing for greater narrative agency, that players should be able to set victory conditions (and seemingly important to your position, influence the nature of failure states as well) inside a wider field of outcomes and more often. I'm saying that is not the same thing as ludic agency, and indeed, can be harmful to ludic agency as it grows by shrinking the possible space for gameplay. A state where all strategies are equally (or roughly equally) viable has just as little ludic agency as a state where one or none are.
1) A player’s facility with “playing the fiction to array the imagined space such that it more likely leads to a new desired state” is a component of play that can’t be decoupled from narrative trajectory.
2) The ability of a player to marshal character build + action resolution dynamics can’t be decoupled from narrative trajectory.
3) Depending upon game engine, the ability of a player to pursue xp triggers and reward cycles will both directly affect narrative trajectory (in the moment of their pursuit) and indirectly because of how advancement will affect (2) above.
I don't necessarily know we're in disagreement here, though I am somewhat unclear on what "narrative trajectory" means here. Given a board state and a goal, trying to best achieve that goal (and given the nature of TTRPGs, possible other, assumed subsequent goals) is the play loop, certainly.
It seems to me that TTRPG that isn’t Pawn Stance dungeon crawling or railroad APs (where narrative trajectory is irrelevant or the control of which has been settled before play), narrative trajectory cannot be decoupled from the above.
I don't think I have sufficient understanding of your point to dispute this. I think what you're calling narrative trajectory is the same thing I'm discussing when players go about declaring goals? I agree that assessment is necessary for gameplay: you need a metric to be able to produce a strategy, outside of pure exploration play, which I think is a pretty unstable state that generally devolves into more conventional play quickly. That is, using a mechanic for its own sake without pursuing a goal, which tends to quickly become adding a requirement to use that mechanic to some other goal.
EDIT - Quick addendum. Texas Hold ‘Em (poker) has a huge dimension of skill that isn’t related to risk assessment or odds of any particular array of hole cards + face cards leading to “the nuts” (best possible hand). That skill is related directly to my (1) above. Players “tell a story (in order to leverage it)” with all of (a) their betting patterns, (b) the historical hands they’ll play and when they situationally will play what hands, (c) their willingness to, and capabilities in, misrepresenting their hands (which is directly related to self-assessing (a) and (b) and leveraging that information). “Generating a fiction (a metanarrative about the player’s boldness, “straight-play,” and tendencies that play will reveal and other skilled players will attempt to leverage) and playing that fiction” of (a), (b), and (c) above is a massive portion of skillful execution in poker.
You're describing a few different things here, none of which I would consider narrative. Adding a meta-game (a tournament) to a game changes the results necessarily. Strategies have to span multiple, repeated plays, which moves the game away from optimization to game theory. To be completely honest with you, I find poker deeply frustrating for the same reason I find fighting games frustrating: the proposed level of mechanical skill necessary to play the "actual game" is huge, and the activity isn't particularly interesting without being played at that level. That, and I think most gambling games rely on emotional valence of loss/risk tied to money to portray themselves as more interesting than they are. That's a pretty divisive issue in gaming in general though; Shut Up & Sit Down in a recent podcast mentioned struggling with coverage of mahjong, precisely because any stance on gambling would alienate about half their audience.
My tastes aside though, assuming players have the appropriate ability to calculate odds and the relatively value of their board position compared to the field of possible board positions, what you're talking about is fundamentally adopting the correct meta-game strategy or, assuming that problem is knowable and solved, yomi. I don't think it's necessary to yield a narrative component to either of those: when faced with yomi, you're trying to find the quickest way to break it into a state that does yield to conventional strategy for as long as possible, or if you can't find a break that way, to continue it as long as possible until such a break can be achieved.
