As I mentioned in a subsequent post, the explanation of play to find out found in Blades in the Dark feels quite similar to my existing understanding of emergent story.
There may have been all sorts of other discussions going on prior to and concurrent with what was written in Blades that take it in different directions, but the basic explanation I quoted earlier and everything else I took from the Blades rulebook was perfectly in keeping with my existing understanding of the concept. I read about about Play to Find Out for the first time in BitD and my only thought was, "Cool, that suits me just fine, it's my preferred way of playing." Nothing since has really changed my mind about.
To my mind, there is nothing particularly special about the questions you're asking above with respect to Hardholder. In my recent Dark Sun game (which was more of a stealth sandbox than an overt one, to be fair, but was certainly a fairly trad game, being run with Mythras) I was very interested to see how the PCs would react to learning that all was not what it seems in the village of escaped slaves where they found refuge. Very specifically relevant to your examples, how they would handle water sources that they need but so do other perfectly decent people. How they would balance pragmatic needs with offering people basic human dignity. Seeing how characters deal with moral quandaries and conflicting priorities has always been part-and-parcel of my gaming, sandbox or not, and I am surprised to see anyone suggesting this is rare or unusual.
Similarly, finding out about characters through play is absolutely part of OSR and trad play among those who oppose complex backstory. My general preference is for PCs to have enough motivation to go adventuring/fit in with the premise of the game, but no more. The game is about what your character is going to do and become, not who they used to be or what they did before. What kind of person they are is something I want to learn about when I see them played. Similarly, when I just played a PC in a very trad (although not especially sandbox) game, I had a concept for my character, and I was interested to see how the character's attitude changed through play and to what to degree his experiences would shape him. Would he cleave to his traditional values, or accept that the world was a bigger, stranger, more complex place? Would he keep up his brave face, or admit to some of his fears? I don't need special mechanics for any of that, and never have.
Which is not say I am opposed to the use of special mechanics, or games built specifically to focus on asking those questions. I'm just saying these aren't new or unique concepts at all and, while I am happy to believe you if you say you haven't seen them in trad gaming, I just think that the fact you haven't seen them doesn't mean they weren't there. As I commented in another thread recently, I believe the hobby is a lot more insular than many people realise. It is entirely possible for two people with decades of experience to have moved in very different circles where what is liked or disliked, played or not played, accepted or rejected, can be extremely different.
I think you would be amply rewarded by actually playing something like Dungeon World or better yet Apocalypse World, with some people that have a handle on it. There are a number of misunderstandings that you seem to be laboring under about Narrativist play.
For Example: Dungeon World does not feature 'extensive character backstory' as an element of play, whatsoever. Players generate a character in much the same way as they would in D&D, picking a playbook (class) and making some decisions about what moves (think powers) they start with from that class. They also have some gear options. From a characterization perspective the player selects a Race, a Gender (this isn't even really germane to anything except RP), an alignment, and a bond with at least one other character. That's it, you don't need to invent some elaborate backstory. In fact the PCs in DW can be just as much wandering murderhobos as they would be in any average D&D game, though it will be hard to maintain that for long...
What distinguishes play in DW, and in varying degrees for other similar games, is the FOCUS ON THE CHARACTERS, as characters, not as cogs in some player's ambitions. You describe there being no need for any rules related to characterization. Sure, that's true for your D&D trad play, because who the characters are, in the sort of sense that we mean when we talk about real people and 'who they are', is irrelevant in D&D! It effects nothing, it is simply color. If a player in such a game wishes to depict their character as brave, crazy, evil, naive, etc. they simply playact that, and they can do so as it is convenient, or not.
In DW there is no precreated world and thus no plot or story arc of any kind exists. The players will describe their characters, name them, pick bonds, and then based on some of those elements the GM will set a scene, perhaps asking a player or two some relevant questions first. Whatever this scene is, it holds some sort of situation which puts pressure on the characters in some way. It may simply threaten them, it may key on a bond, it may present an opportunity, possibly with a cost, etc. This stuff will generate weighty play.
It is easy to imagine a likely scenario, the characters have all arrived at the town of Blackhill, on a river boat, so they're at the docks. The fighter's bond is "I have sworn to protect Smirk the Halfling." As soon as he steps off the boat he sees that some tough looking customers have accosted Smirk! At this point the GM might ask "why did you swear to protect Smirk?" etc. etc. etc.
Notice too how we've already built up a fair amount of fiction, a river, a town, boats, docks, ruffians, etc. There's plenty of standard fare kind of material here to go forward with. Maybe the setting is a bit more fantastically described too, like the GM is tasked with making the world fantastic. While the Fighter is worrying about the halfling, the cleric is being seduced by mermaids, tricky little things, they just like to pilfer things from travelers! One of them seems wounded, and his Good alignment says "Endanger yourself to heal another." Well, he was warned by the boatmen that these creatures are thieves and con-fish, so will he be prudent, or follow his moral code?
I'd also note that Dungeon World basically doesn't have any kind of mechanics that tell you what you HAVE to do. Unlike BW it doesn't have 'Steel checks' and such. If the Fighter protects the halfling and resolves that bond, he gets XP, likewise the cleric could get XP for healing a mermaid, though he may lose his purse as well! Players decide. Maybe the mermaids harden his heart a little bit, he might change alignments later on!
So, most of this is not a RADICAL departure from trad games. What is really different here is the unrelenting focus on player concerns, the way these concerns are put under pressure and tested, and the lack of 'architecting' the game by a GM. Later the GM WILL devise fronts and draw some 'maps with holes in them' to help her frame new scenes and 'bring the world to life' (IE a campaign front can provide an overarching backdrop of action, like "you see a column of dusty soldiers enter the north gate. They look as though they've had a rough week in the Orc Wars!"). Well, maybe the PCs join the Orc Wars, maybe they don't, as in any such game, but it is an Orc War because the Dwarf answered the question "why did you come to town" with "I was made homeless by the Orcs." Maybe he wants revenge?