Important frame. I think any effort that doesn't start with this statement is probably headed for frustration.
I reckon this is true also for education, aspects of economics and many other fields. Besides sloppy and/or cynical work, I believe a lot of the "replication crisis" relates to this. Do we really expect that a relationship between watching TV at dinnertime and marital sex life observed in 1986 Tokyo to replicate in 2021 Berlin? If it doesn't, does it mean that it doesn't exist, or teach us anything?
Scientific academia is sort of premised on the idea that we start from a blank slate, and build up an understanding of a field based strictly in science. It doesn't matter that you already know gravity pulls thing to the ground or that water boils when hot. It must be stated scientifically, tested and theorized.
Well... realistically, from this perspective, we know almost nothing about managing people, teaching, lots of things. Yet, we do manage to do them somehow. People all over the world created domesticated cultivars before Gregor Mendel. Science isn't the only framework for knowing things.
Writers working on their process don't generally go to "empirical research." They read Stephen King, or one of many other authors that speak about their process. They find one that feels compelling. Often, they describe things in terms like "earning the respect of the muse." Usually, it's a poorly supported framework made of a smattering of methodology, random bits of advice, unique terminology and some innovative semantics. Sound familiar?