I assume anyone seriously in the book business has a fairly well-calibrated idea of roughly what a book cover should look like to sell a book. And I imagine if you really studied book covers for various genres, you'd see a lot of pretty common patterns.
I don't know about the book business. But in other fields, it's shocking how often marketing does not provide a marketing brief when asking for artwork. Some more professional artists will prompt and help put one together, but that uses up quite a bit of time = budget.
DRAFT: conceptual work of art that the artist enjoyed making & might impress other artists
FINAL: a book cover, a product of commercial design, designed to sell a book
It's really not shocking that they went with the latter.