I don't have any studies but it certainly seems healthier than the high-carb, low-fat diet which was promoted by the medical establishment for so long.
It also completely ignores the very personal nature of a diet. What's easy to follow for one person will be very difficult for another.
And if you're rating a diet for heart health I'd like to actually see the rates of heart related illnesses for those following the diets.
Although, many of the individuals are nutritionists at reputable scientific institutes, so hopefully their opinions are informed by scientific studies. There's no guarantee of that, of course, but at least their credentials are stated up front (unlike the many nutrition experts you'll find in any given message board).