I don't know about that article.
I understand the study but telling older people that it is too late to exercise, that it won't do any good, doesn't seem right. The article focuses exclusively on heart and blood vessels but there are other benefits to exercise.
Strength training increases bone density and reduces risk of injury for example. Aerobic exercise stimulates blood flow to the brain and extremities apart from whether the heart grows stronger. Fresh air. Getting out of the house. Enjoying nature. The mental benefits of staying active. There are many other benefits.
Sure, it is better to exercise your whole life but I'm not about to call my mom and tell her to stop walking every morning because she is too old.
-Tim-