Now, you have to understand that I'm a lumper, not a splitter. I look at the big picture rather than the details, the theme rather than the individual pieces. So while the article was really a meta-analysis of data from 15 randomized controlled trials regarding diastolic blood pressure and 16 randomized controlled trials regarding systolic blood pressure vs epicatechin, a monomer flavanol found in cocoa (chocolate), it turns out that pure epicatechin can increase nitric oxide which leads to vasodilation while decreasing vasocontricting compounds.
70-80% cocoa solids that has been espoused in other studies. So while this study isn't recommending Americanized milk chocolate, it's quite possible that a palatable 50% cocoa will be adequate at least for blood pressure lowering purposes.