I'm not arguing with your basic point - in fact, "but some people are better at expressing their intent in code than in prose" instantly occurred to me, as well - but why should "it's always possible to leave holes and stubs to be filled in later" not also apply to natural language?
I, at least, have always written in that way - essays, teaching materials, letters, long-form narratives, (and now, recently) specs for the AI-gods, doesn't matter - I get the bits I'm sure of down first, and then tinker (cut-and-paste, do more research, add or remove material, write bridging sections) until I'm able to connect them together.
The most frustrating English teacher I had in high school required us to turn in an outline a week before the essay was due. I did it for the first assignment, and was marked a B, with a comment along the lines of "this was very good, but it deviated from your outline". Which, well, of course it did, because I bloody learned something while I was writing it! The next time, I wrote the whole essay ahead of the "outline" due date, which led me to discover WordPerfect 5.1's "Generate Outline" function, which led her to the mistaken impression that she'd taught me something besides disrespect for authority.
That's not quite a digression by way of personal anecdote, because I wonder if you were taught writing by someone like her? Prose doesn't have to be composed (in both senses of the word) like that. In process, it can be just as shaggy and stubbed and non-linerally referential as code. Furthermore, AIs (I am finding), work quite well with a process like that: I'm constantly telling it to "put X into Deferred", when I haven't yet got something worked out in my head.