From what I've seen described here, even most of the player facing games don't go that far.
I'm sorry, but I reject the idea that the DM coming up with stuff on the fly = "Play to find out what is in the DM's notes."
Oh believe me, it felt very . . . odd, off-putting, cognitively dissonant, maybe . . . when I thought about it the first time too.
What finally sunk in for me is that I realized that it didn't matter what my
agenda was. I didn't
want the players to have to expend time, resources, action declarations going around trying to figure out just how, exactly, they could pull off "stealing a boat," to use your earlier example. I didn't
want play to turn into a tug-of-war with the players trying to drag information out of me.
But ultimately, even if I completely created the scene framing off-the-cuff, there was still just a metric ton of information that the players didn't have access to---i.e., "notes," whether physically written down in my OneNote campaign folder, or just floating around in my head.
And it's not that the players suddenly decide, "Ah! I must now perform every action necessary to get the GM to divulge those notes!" At the table it feels much more organic, right? The players perform Gather Info checks, they have their characters watch the docks to see the guard rotation, they scry on the harbor master, they sneak into the merchant's headquarters to look at shipping manifests, etc.
But really all of that is ultimately just a means to the end---to get all that info out of my GM notes and into their hands.
I do think that "Playing to find out what's in the GM's notes" is a bit of a . . . needlessly negative descriptor for the process, shall we say. But even if I don't necessarily like how the term is couched, it's pretty accurate nonetheless.
But I think it's very much tuned to the newer zeitgeist of RPG play, which is to "GM from abundance, rather than scarcity." Like, there's this almost perverse need from the "Philosophy of the Old School" to hide information from the players, or only dole out information in a parsimonious fashion.
Like, what's really the "fun"---the figuring out the
how to steal a boat from the harbor, or the actual stealing of the boat
to see what happens next?
And I'm not saying that both of those can't be fun---but I think there's a strong pushback, largely derived from the indie game segment of the market, against the "GM-as-information-miser" trope.
I also reject the idea that improv = DM's notes. Those don't jive with my experience and how people on both sides of this issue describe how things work in RPGs.
Yeah, this one's weird too. Like, thinking of even a basic interaction between a barkeep and a PC---obviously everything the GM says as coming out of the barkeep's mouth is now part of the fiction, right? That's all "improv," in the moment fiction generation.
And it happens all the time in RPG play. Like, practically non-stop.
But I think it goes back to the whole concept of when an actual game mechanics loop initiates. When do players usually indicate they want to invoke the game mechanics? When they want something, and there's some debate as to how to determine if what they want ends up being true or false.
A simple improv conversation between a barkeep and the party can establish dozens upon dozens of fictional "truths," none of which the party disagrees with or takes issue with. In fact, some of the established truths may provide hooks or spin-offs for the party to grab on to.
But as soon as a character says, "Does this barkeep know anything interesting?"
In traditional play, that's 100% the call of the GM. Maybe the GM's notes say, "This barkeep has no useful information related to the party's quest."
Maybe the GM notes say, "The barkeep may provide information about X, Y, or Z, depending on reaction rolls."
Maybe the GM has no notes written at all, but says, "Oh yeah! He totally knows something! Blah blah blah MacGuffin treasure blah blah."
Or you take something like Ironsworn, which says that you make a check, and based on the level of success, the bartender may provide 2 bits of highly useful information, 1 bit of moderately useful information that also contains a potential obstacle, or zero bits of useful information and some other complications arise.
This completely takes the result out of the GM's hands. Even if the GM then narrates something (s)he hadn't prefabricated, it was a result of the rule being invoked, and all participants agreeing to abide by the stated rule structure.
But what's really happening is that Ironsworn is going out of its way to bypass all of the "sussing out what's in the GM's notes" bit.
The issues most traditional GMs raise with this are 1) that it basically negates GM pacing---the GM can't "draw out" the mystery for too long if the game is forcing them to provide information; and 2) it means the GM can't pre-arrange or sequence the info drop scenes/encounters. For a certain GM style, this probably feels like a punishment to be avoided.