Is this really an "understood" truth? In our own study for our own site, we found nearly everyone scrolled the page all the time, and that seems the be the case with every colleague I've ever talked to as well. Who goes to a page and says, "fuck it, that scroll wheel is just way too damned difficult"?
The thing that is puzzling to me is the whole thing about people scrolling & responsive design. How do you design something to avoid scrolling when your layout is designed to accommodate any screen size? It seems like those concepts are in conflict.
However, as the author admits in the comments (after being corrected by a reader), he has interpreted the results of the source incorrectly. The cited report actually only says that "Web users spend 80% of their time looking at information above the page fold. Although users do scroll, they allocate only 20% of their attention below the fold."
My guess is: if you capture their curiosity, they will scroll. Otherwise, they probably won't. Simple, I know, but I'm going with it.