I was also skeptical, but I was thinking about lifestyle. I was thinking that people doing manual work like construction workers and farmers may not have the time available to drink threee cups of coffee per day (In the US, farming is actually the most deadly occupation per-capita - or at least that was true a few years ago). In contrast, desk-workers can drink coffee while we work.

So, in general, I was guessing that there are lifestyle differences that cause both the differences in health and coffee consumption.

Your point about geography is also a good one. I've seen several articles on the topic that many scientific studies are biased by their reliance on "WEIRD" research subjects (Western, Educated, Industrialized, Rich, and Democratic). It's easy to believe that these underlying studies were, too.