Question https://musicfans.stackexchange.com/questions/12245/in-which-of-his-works-did-mussorgsky-include-features-of-human-speech was migrated to MusicFans with the option "Not suitable for this site." I'd be curious to hear a bit more elaboration on why it didn't fit within our on-topic parameters. Granted, it could have been a bit more clear (the topic of speech-to-pitch imitation wasn't explicit), and the OP certainly could have done more homework (the question amounted to "wikipedia said ___, with a citation, and I didn't look up the citation, but I'd like to know more"). So the question isn't a great role model, but it still leaves me puzzled why it should be considered off-topic. One might imagine a better-worded, better-researched version of "I read in SourceX that ComposerY used TechniqueZ, [and for the purposes of this imaginary question I did my own research and came up empty]. Which works of ComposerY was the author of SourceX referring to? How did the composer use TechniqueZ?" This seems very different from your average "list" question, like "Can you give me some examples of Beethoven's works that are in A major." It's a narrowly-scoped question about a specific technique in the work of a specific composer.
At the end of the day, this question was asking for a list of songs that fit a criteria which is explicitly off-topic under our general finding lists of songs close reason hence why it was considered for migration. As for how the migration happened, since we don't have direct migration paths to any site right now outside of meta the mods had to do it. In this case I migrated it after being alerted to it by a few flags from users.
I tend to also look at questions like this as if they were asked about different musicians/artists if they would fit on this site and to me, I though of a question I think is in a similar footing which would be "Which Beetles songs include non musical sound clips in them?". To me make it pretty clear the music fan's site is more appropriate and how that "Finding pieces" close reason would make sense otherwise.
Perhaps there's a couple of issues here...
Whether it's a question about music history or composition, or a bit of 'trivia'
There's probably always going to be a bit of a fuzzy line as to whether something is about music history or composition, or just a piece of artist trivia. Some things could be either: Pacific State - Is this out of tune, or is it a sophisticated performance playing with temperament? springs to mind as something that is an illustration of a compositional (or production) technique, and is also a bit of trivia. That question could probably live on musicfans, and it's probably fine here too.
Going back to the Mussorgsky question, Perhaps the brevity of the OP makes it hard to see how it relates to music history or composition in a substantial way.
Whether it's a prohibited 'list question'
I'm not really sure I can see why this question is a 'list question' in a way that makes it off topic.
https://music.stackexchange.com/help/dont-ask states that users should "avoid asking subjective questions where you are asking to list something" (emphasis mine). But it's entirely possible that answers to this question can be quite objective, if the historical documentation is there.
https://music.stackexchange.com/help/on-topic states that questions should not be about "recommendations of pieces to listen to, study, or play, or that meet particular criteria". But I don't think this question falls under "recommendations" in the sense that I understand it there.
Note that there many examples of questions asking for examples that fit criteria that have been well-received and remain open - here are just a very few examples, that took seconds to find:
Those are just a few examples, that took seconds to find. The point is often made that finding the odd example of a question that has remained open doesn't necessarily mean that such questions are generally seen as on-topic, but there are so many of these questions that this doesn't seem a relevant point here - we can see that list questions can be fine, as long as the request for a list is made as part of a substantial on-topic question (which is perhaps where the Mussorgsky question falls down).