These programs are great for sitting down and writing with no distractions, but if you have a setup with directories full of word docs, text files, various graphics, even excel sheets all related to what you are working on that you need to refer to and cross-reference, they are less useful than an older version of Word or OpenOffice/LibreOffice. And they are difficult to export, share... there's a reason we don't use typewriters anymore, or DOS programs whose output is confined within a single program.
That looks like a different type of writing, perhaps research or business writing. Wordstar like editors that bring simplicity and a distraction free environment are best suited for creative writing.
I've found trying to find a distraction-free editor a distraction in itself. I'd bet money that most authors using an old word processor had some external reason to use it (cost, availability, editor compatability) and just stuck with what they know.
A large fantasy adventure could easily have supporting documents with cities stats, characters, races, maps etc.
It could have, but George R R Martin famously uses Word Star and he surely has all that.
Then again he's also about a decade late with the next book
GRRM could use clay tablet and it wouldn't make any difference on his output.
If you want output, Stephen King has used many processors, he doesn't care aparently as long as he can focus. Brandon Sanderson uses Word. The tool doesn't seem to matter.
My point exactly; sci-fi you even more need to refer to accurate statistics whatever they may be.
Unless the fleet travels at the speed of plot.
Back then we were far less shy about printing things.
After reviewing a few options I think "Just print it out" is still the best choice for long term archival. The density is not high however the hardware requirements being just one mark 1 eyeball(hardware that self replicates and has been stable for millions of years) makes it the clear winner in almost every case.
DoD approves this idea
(Recall the literal warehouses of papers related to projects in Kelly's book and Rich's memoir)