I think the problem is that it is complicated. Many things have been implicated in high blood pressure, anything from nutrient intake to plaque buildup in the arteries. Nutrients like calcium and magnesium have also seemed to help control high blood pressure and so does exercise. Levels of one nutrient influence levels of others as well as needs for levels of others, such that it all becomes such a big tangled web of confusion that they haven't yet sorted it out. Here is an article on potassium that touches on some of that: http://www.webmd.com/a-to-z-guides/potassium-k-in-blood
For myself, I feel that decent levels of potassium intake may be good and are probably not bad so I try to eat decent amounts. But I think it's far too soon to assume that lowering of blood pressure via high intake of potassium might directly influence cardiovascular risk to a large degree. Higher blood pressure may be correlated with heart attack risk due to a lot of hbp problems being causes by plaque buildup. But if you get your blood pressure down via manipulating potassium and salt intake, but the plaque is all still there and building, then this may turn out to do nothing whatsoever to improve your cardiovascular health. Because high blood pressure could just be a mostly symptom of plaque buildup and cardiac probs, but it may not be the actual cause. In order to truly solve a problem you have to get down to the root of it and I don't think we know for sure the root of it yet, although inflammation may well be a strong contender at this point.
Also, I see no study citations in the original cited article, so I am not sure how we know that any studies were 'detailed' or even particularly relevent. To me, it is not enough for them to just say 'studies show' while giving not references at all. So I am not monstrously impressed with the article as major scientific evidence of anything. That article is enough to portray a basic idea ot the public. However, I think the jury is still out on if eating more veggies and fruits will automatically cause more good then harm just because they have potassium in them. They also have sugar, which could lead to increased inflammation and exacerbate many with already existing blood sugar issues, which could cause more problems than the potassium solves. And studies I have seen comparing actual real life fruit and veggie intake with health issues have NOT been able to find any obvious benefit to eating more fruits and veggies.
One of the dangers of having a preexisting theory is that one tends to cast around and only notice data that fits that theory. This is why epidemiological studies are such a dangerous tool to use. Okinawans are different from americans in millions of ways so the number of uncontrolled variables are astronomical. But I would like to point out that there are a number of groups that eat little or no fruits and veggies but still have healthier cardiovascular conditions. If it were all about potassium by itself, this would not be the case.