Joslin does use recent information from the American Heart Association and the American College of Cardiology for pushing for low fat. That information is from November 2013 and does not reflect the study published in the Annals of Internal Medicine in March 2013. Even many cardiology doctors are not convinced by the study and will wait for additional studies before they accept saturated fats as being safe.
While the most recent study is favorable to saturated fats, the Joslin blog author takes great care to say that the complex statistical relationships is beyond our knowledge. Whether you believe that many studies have shown that eating mono- and polyunsaturated fat does not cause heart disease is entirely up to you. The author says the same can't be said about saturated fat.
The last sentence above is the reason for my stating that the blog author still believes the faulty study from the 1956 “Seven Countries Study” led by Ancel Keys, who started the demonization of saturated fat. Again and again this study has been refuted, but many in the medical profession and especially registered dietitian nutritionists like to use this as proof that saturated fat is bad for us.