Creativity doesn't work that way. You'll literally inventing new things. It would be like saying, "let me plan out how I will innovate." Makes no sense.
I very rarely know what I'm going to write until I start writing. I don't even outline anything. I just start writing and relentlessly edit as I go.
I do the same thing for 1,000 word blog posts as I do with 400,000+ word course scripts.
If anything editing is more important for the larger pieces of work because in order to cleanly flow to the next lesson or section of a course the prior stuff has to be pretty much in its final form.
I'm not really a big outline person either for either writing or presentations. I almost always have some idea where I'm going though it's not unusual for that to diverge.
A good way to think of creative writing, if you're a technical writer, is to imagine attempting to write a textbook when you don't know the subject at all, and the "demand" from each new paragraph causes you to do the research necessary to acquire the knowledge necessary to write it.
How would you even structure a thing like that, in advance?
How would it ever attain a sensible shape if done a paragraph at a time, when something you learned while doing the research necessary to write paragraph 100 invalidates everything you wrote before it, or causes a complete restructuring of your mental model such that you realize the topic should be presented in an entirely different order? (And then you realize that again, and again, and again...)
A similar thing occurs in investigative journalism. How would you know how to present a story—know what story you're telling, really—before you know all the key facts? In est, before you've completed your investigation? You could certainly write notes about what you might write, but those have little to do with drafting the final story.
For many disciplines, the actual research involves field work, performing experiments, etc., and the thesis is primarily about reporting on that process and connecting it to the pre-existing body of research. For other disciplines (for example, philosophy), the text of the thesis is all there is to the research. Maybe the later is more like creative writing and the former more like technical writing??
(My uncle did a PhD in creative writing, his PhD thesis was a novel.)
The advice to "don't edit while you write" usually comes after the advice to "make an outline" before you write. You are supposed to figure out how the pieces fit. Then quickly write it all out. Then edit edit edit.
The general idea is that is easier to edit afterwards than to edit on the fly. Its true for me.
Same thing with writing. Yes, you are literally making things up and inventing new things, but that doesn't mean that one is writing freely and not needing to edit along the way. Outlines give framework, and editing gives time to reflect and plan things that might not have been planned in the beginning. I'm not saying that no one works this way - just sits and writes, or does freehand paintings (I do this last one, even with watercolor, and accept a certain failure rate) - but how one works doesn't really reflect on their creativity nor how their creativity works.
Not that I know how the mind of a great author works, but it seems that it would be difficult to write a great story without having some solid idea of what the final product should look like before you start. Like creating a product, maybe they pivot a lot after realizing that something doesn't work well (Margaret Atwood apparently did that for a book once, completely started from scratch after realizing that she had chosen the wrong point of view for the protagonist). BUT it's difficult for me to imagine they don't actually have a good solid idea of the story they want to tell before they start writing. If not book by book, then at least chapter by chapter. But hey, I'm not an author, maybe their minds really do work differently. It's possible.
I guess my overall point is that I don't think having a solid idea about what the final product should look like is the reason why authors have the "never edit while drafting" because I think they also pre-structure their ideas, and diverge on "editing while drafting" for some other reason. But of course I have no data or evidence to back this idea up.