For example, when they talk about the introduction of the proto Dock in Mac OS, they say "no major changes in UI". But when Windows introduces the Start menu and task bar that's changing the UI "completely". Then come the incremental UI refinements and color changes that coincide with new graphics capabilities, again this is heralded as being more of the same for Mac but radically different with each version of Windows. Looking at these screenshots which show similar trends in UI development side by side and coming to wildly different conclusions in the face of those similarities is just a stunning display of cognitive dissonance.
The change to Metro would be the only big jump where the article is actually right in asserting a real change, if we'd be willing to forget the fact that Metro (or whatever it's called now) is nothing but a thin veneer you have to get past in order to access the real Windows, which is of course pretty much a clone of its predecessor.
All this just to explain a conclusion from an anecdote, a conclusion which the article itself proves wrong unwittingly. Even if we accept that OS X users don't buy books about their OS and don't rant as much (which I find particularly out of touch with reality), that's because there are vastly more Windows users around. Because the numbers are so great, there are also a lot of Windows users who lack the tech intuition but want to learn, so they buy a book about it. OS X clientele is just by and large different. That's where the real difference lies.