Today I frame this concern within definitions of fiction and nonfiction writing. I prefer the less troublesome distinction of prose and poetry, admiring how each incorporates its facts with fictions.
The lesson from a graduate Nonfiction Writing seminar, taught by a journalist from the Times, was to reserve disbelief for all writing; what claims to be fact was probably composed by an overwrought researcher in an effort to please an editor.
This was a lesson I'd begun to learn much earlier, as a history student, and met again in literary theory. All forms of writing aim to please some editorial eye, acknowledged or hidden.