It seems to me, gingernut, that it's another example of pulling together a committee, then coming up with a recommendation that keeps the majority happy. So it was decided that seeing as how the downside of drug therapy is low, the threshold for treatment could be lowered. And then if you lower it enough, then everyone over 50 will have a 10 year cardiac disease risk high enough to cross the threshold.
Unfortunately history shows that in most of medicine if you think you have the final answer, it'll turn out in the future to be completely wrong. (Think "mammograms" and "PSA")
And today we are often guilty of assuming that the most recent "study" is correct, even if it negates the previous 25 studies. That's usually because the recent study was not one at all, just a "meta-analysis" (i.e. a rejiggering of the data).
Rant off. I'm late for bed!