My like was because this is not far off from my aforementioned "there's been a murder but you have a quantum murderer until the party declares who the murderer was" issue. That is, I don't at all mind (nor consider it "easy mode") that the player can declare elements of the setting in general. But certain kinds of them break any semblance of groundedness or verisimilitude for me, and those things can't just be "player declares whatever makes sense."
I just can't wrap my head around the idea of "solve a mystery" where the "solution" is invented by the players. That rings as so obviously, inherently hollow that I literally cannot imagine enjoying an experience where that's how a mystery got resolved. How can you collect clues and draw valid inferences when not just the clues but the inferences themselves are causing the truth? It would be like if an absolutely omnipotent deity (that is, one not bound by the rules of logic) tried to do science. How can you perform an experiment and record the results in order to learn something when you, personally, are directly making the results happen, and you, personally, are creating the true state of affairs that the experiment is attempting to ascertain? Indeed, you personally are deciding what logic itself is permitted to relate? That's just...not solving a mystery. It's re-writing history so that whatever you believe to be true not only is true, but always was.
We've talked the mystery angle to death here in the past and you've gotten a few posts about it in here (with
@Ovinomancer mentioning The Between...I encourage you to look into that and give your thoughts on how its sort of a
Story Now meets procedurally generated mystery play).
However, I'd like to point out the following:
* Spout Lore isn't about 1st order mystery creation. Mystery creation may be procedurally generated and may procedurally unfold downstream of a Spout Lore move, but it isn't fundamentally about that.
* Spout Lore is about
content creation (setting and/or situation and/or character). I think your feeling on this is pretty illuminating because Story Now games that are low prep or outright No Myth (Story Now games vary on the continuum of prep and backstory and structure vs freeform) are engineered to create content during play in the exact way that Spout Lore does this.
Your second paragraph is one shared by a certain cross-section of the gaming community, but it is not shared by me.
Spontaneous content creation happens in all games, whether its a a Reaction roll to find out what this kobold is like in a Moldvay dungeon, a Random Encounter roll in an RC Hexcrawl, or a Streetwise move in 4e D&D, or a Spout Lore move in DW. The logic of the gameworld that we're all collectively creating is imbued only with the internal consistency that we give it (or that we fail to give it) after the participants have had their say and system has had its say. There are no inherent causal chains because the shared imagined space fundamentally does not exist (as we all know). This isn't a model that we are parameterizing and then letting the algorithm perform a run (and then rejiggering parameters to curve fit if things are unphysical). We're humans and system manufacturing all of this in real time.
So whether you feel sensitive to a causal chain (eg this forge only exists in this particular instantiation because of this spontaneous Spout Lore result vs this forge only exists in this particular instantiation because of pre-play prep) is a autobiographical feature of your cognitive disposition as it pertains to content generation in TTRPGs. It isn't an objective thing (just like a feeling of verisimilitude).
If we fail as a group to achieve physical coherency, backstory coherency, or thematic potency/procovation with our newly introduced content (whether its a Reaction Roll with an NPC or a Random Encounter roll in a Hexcrawl or any of the myriad of content generating procedures in a PBtA game like DW), that failure is shared by the group collectively. We should own it and resolve it.
* After the new content is created during play, we either (a) chase it like a crazed dog after a firetruck or we (b) repurpose/reorient it so that we're inclined to do (a).
* But this is principled, structured content creation with constraints and rules we must observe.
The game is littered with this sort of principled, structured, procedural generation of thematic content. If a GM or a group doesn't like this approach, you're going to have to do some significant drifting in order to get to a play paradigm that is more palatable for you.