This study examined only results - a heart attack or stroke - not whether the patient had vascular disease. The heart attack or stroke could have been caused by increased blood coagulability, if the subjects were using hormonal contraceptives.
I can’t find a link back to the original article.
He does state that the end point is heart disease not heart attack or stroke. He also says that the results were stratified for other common causes of heart disease. What those statements mean remains a mystery.