Uh, sure, you can work from a set of principles, agenda, techniques, etc. that is not coded into a game. I agree that if a game provides an interpretation of what it is about, that it articulates it, then it likely, almost by definition, excludes other interpretations. Wouldn't that be true of anything that has greater clarity? Its pretty much the DEFINITION OF clarity.I do not find this with 5e. It's a genuine puzzler for me: the implication that some DMs hit points where what follows isn't clear to them. Other posters described that "the actual cognitive workspace a GM is inhabiting during play and the conversation is pushing toward yields consequences that are profoundly far away from unconstrained or anarchy" and for me that is true in 5e.
The closest I've come to not knowing was two sessions ago, where the player-characters were all down (due to a cursed necklace of fireballs) and two non-player character allies were standing. Due to complexities in the situation, it took me a couple of minutes to parse what to say next. Afterwards, one player felt that one of their foes, who was also standing, should have made a more vicious move. In the moment, I felt that relied on information that foe wouldn't have. Everyone else agreed with what I narrated.
I feel sure you are right about word count. As I hoped to explain above, I very much feel it is right to say - "It is preferable for an RPG text to articulate principles." At the same time, I know that I cannot say - "DMs is not influenced by principles, unless they are articulated in an RPG text." I'm not meaning to embrace the Oberoni Fallacy. Rather I see external influences as unavoidable, and in fact virtuous in play. Essential for play to occur. There must be something left unsaid between text, system, and fiction.
[It strikes me that a game that clearly and extensively articulates its principles works to exclude other interpretations. On first reading, Stonetop looks like a good example of that.]
After GMing 1000's and 1000's of sessions over decades I'd say that there have been a LOT of situations where there was a question about 'what follows from this'. I attribute a lot of that to game systems which are not very clear, personally. I have not had such a problem with, say, DW. I mean, you could follow with one of many things in rather a lot of cases, but its always pretty clear if a response, a move, is at least appropriate, and how to rate it against other options that spring to mind so you can pick the best one.
Frankly, my personal view of 5e is that it is generally in the same boat as 2e. Its a game with a fundamental design based around a GM who provides a structured and bounded environment in which are embedded a series of challenges and incentives which work together to define the process of play and answer questions about what should happen next (IE what the GM should narrate now).
Unfortunately whomever wrote 2e, back in 1989, was writing from a MUCH less sophisticated set of RPG design techniques (and TSR was not exactly at the cutting edge of what WAS state of the art even then). It is a HIGHLY incoherent design, and this has been subject to pretty thorough analysis several times here in my recollection, so I don't feel like it needs much additional commentary at this point. The problem with 5e is it simply doesn't FIX THE PROBLEM. Yes, it is a MUCH cleaner and tighter system in terms of the nuts and bolts of the "how to decide of the PC climbed the wall" sort of stuff. It also reduces the contrast between the promise of heroic fantasy and the reality of single-digit-hit-point adventurers, and such. So its certainly a better game in some respects.
OTOH the core problem still exists, the player is handed a vision of playing Conan the Barbarian, so to speak, but much of the mechanics of the game seems aimed more at keeping that kind of thing in check! Honestly, this is why the fixed DC skill system in 5e is, to me, so blazingly nonsensical! If you want a game of heroic action fantasy, then AT EVERY LEVEL the PCs should be executing heroic action fantasy. The difference between level 1 and level 10 and level 20 is the trappings, basically. But the "levels count for nothing in calculating DCs" ranking system totally undermines that! I don't honestly know what 5e is ABOUT. It says action fantasy, but the rules pretty much tell me no. I grant you, its less of an issue than in any other (non-4e) edition, but it is still pretty problematic (and then casters get to carve their own little doorway into gonzo).
Anyway, I think this discussion has clarified a couple things in my mind about working on my own game design. I am more clear than ever as to the NATURE of what level progression should bring, amongst other things.