As three examples of things I'm very interested in, Bruce Sterling is a major successful author whose novel The Caryatids came out from a major publishing house (Del Rey) about three years ago. Greg Bear's Hull Zero Three came out about two years ago. And, of course, "Corey"'s Leviathan Wakes came out 14 months ago and the sequel is already out.
Big publishers long ago abdicated the short story collection market (which is a whole other rant) but it was almost a law of nature that a mass market paperback was released one year after the hardcover release of a regular house's novel, give or a take a month or two of great or poor sales.
Now, aside from Amazon being a digital marketplace and so naturally biased towards the digital, even assuming their claims are accurate, not one of the three books above has had a mass-market paperback edition and so I have not (and so long as that's true, will never) buy them. But it doesn't surprise me that most people buy an ebook when there's no %^#$(! choice about buying the mmpb. It's no feat to outsell something that doesn't exist.
So the corporate market shapers once again demonstrate how much "choice" we "consumers" have to shape that ol' "laissez-faire" market place.