Imaro
Legend
So far all intents and purposes, "protagonism" is a word being used as a placeholder for a nebulous grouping of characteristics shared by some games but not D&D? If thats the case have those characteristics been defined in this discussion at some point? If not how can a discussion take place if the thing we are discussing is ill-defined and vague in meaning?Correct. What you describe in your second paragraph is a general property of RPGing.
Whereas, as @Ovinomancer has explained, by player protagonism he is referring to a phenomenon that is a particular property of only some RPGing.
Hence what he is referring to is not what you describe. It is the sort of approach that is quintessentially found in such games as Prince Valiant, Maelstrom Storytelling, HeroWars, Burning Wheel, DitV, and most PbtA games. Ovinomancer's own experience of this sort of play is, I believe, primarily with Blades in the Dark.
One feature of those games, relevant to this thread, is that the GM's pre-play notes do not serve the function of establishing the principal parameters for framing or for action resolution.
Edit: Instead of discussing "protagonism" perhaps a discussion of the specific characteristics that define the word should be the topic...