While I accept the line of reasoning at a high level, it does not answer my question. X can be of the kind "worst possible failure" and "disastrous consequences" without that meaningfully reducing my options for what I can say X actually is. Subsets of an infinity may still be infinite!
I think my answer to
@EzekielRaiden touched on this, but in a bit shallow level. I think this asks the relevant question so sharply it warrants a bit more investigation.
The problem posed is that
even given all the constraints the narration and principles ensuring a mechanics to be "diegetical", we still have a enormous number of posible narations. How to chose one of them? The naive answer would be that it shouldn't matter, as all narrations has already been established to satisfy all relevant criteria. However as demonstrated by the example of "take the one you prefer" the methodology chosen here can still compromise the property of the mechanics being "diegetical".
This is indeed a non trivial problem. How to neutrally decide among such an huge number of options. I am proposing a human judge that try to stay neutral might be the best option we have available to us - not just in terms of speed and practicality, but indeed in terms of limiting bias/groundedness.
To take a couple of the alternatives - one is to add extra constraints via oracle until you after an exponential reduction are left with only one option. Even if we ignore the practicalities of narrowing down to the choice of words with this method, we still have the problem in that we introduce hard to reason about biases in our choice of questions, and the corresponding probability distribution we create.
Another might be to pick out a limited sample and select one of them randomly. Like pick 6 possible outcomes and roll a d6 to chose which to go for. Again we have the bias of choice, and again we could get into situations where we unintentionally introduces skews. For instance if someone using this method think it would be good to in general introduce an outlier in this set of 6 to give such outcomes a chance of happening.
Allowing a human to judge strongly limits the likelihood of such probabilistic issues to become visible. Indeed in terms of groundedness the unintentional
order a human is likely to introduce compared to real randomness is likely highly preferable, though not fully ideal in terms of "diegetical"-ity.
I still think the mechanics can safely be called "diegetical". That the implementation of it has flaws in terms of human imperfections I think should not reflect back on the mechanics itself. This similar to the fact that no dice is perfect would normally not be taken into account when analysing the probabilistic features of a rulesystem.
Setting that aside, is there any causal explanation traceable in the text I cited for why Dance sometimes has the outcome "lust" and other times "wonder" or "telling a story" beyond the player intending that their skill use should have that effect?
This rules text would probably not pass muster in a turnament setting in this regard - but as an interpreting GM my reading of it is that the "desired emotional response" of the game text refer to the
adventurer's desire, and as such it would be whoever is responsible for determining the adventurer's desire that at some point must provide information about which of these it is. That would typically be the player. Then it would typically be a responsibility of the GM to ensure nothing in the fiction narrated at any point prevents a diegetic causal explenation. A causal explanation need not actually be identified.
Edit: I think I misread your question. No I do not think the game text provides any aid in producing such a causal explanation. But the outcomes presented do not present me with any particular challenges with seeing possible causal explanations based on my experience as a human being - so the game text hardly need to provide me such support.