Thank you for your post, which raises some interesting questions. Of course at this point it is not known if Roberts died of a heart attack, although the smart money is on a cardio-vascular problem - heart attack, stroke, aneurism, etc.
The first question is whether the Agatston score is as good as it's made out to be by Doctor Agatston. Another question is whether it is skillful in the case of Roberts himself. Probably none of the people who were studied were eating half a stick of butter a day, along with lots of flax seeds, extra light olive oil, and who knows what else.
I'm not a doctor, but a quick search on Wikipedia turns up that the most common cause of sudden death in people over 30 is coronary artery atheroma (arteriosclerosis), but other common causes are genetically determined or at least have a significant genetic component. I suppose some of these are easier to detect (hypertrophic cardiomyopathy perhaps?), so we can probably rule them out for somebody like Roberts who constantly monitored his health and bragged about how healthy he was. Other conditions are probably more difficult to detect with standard tests.
You know the drill - If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
And, while this is an accidental exception, future open threads should start on Mondays until further notice.