I really like everything Uri Alon (last author) publishes, but these types of studies have a history of inflating genetic contributions to phenotypes. Decoupling genetics from environment is not easy as they are both highly correlated.

In fact, the article discussion states: "Limitations of this study include reliance on assumptions of the twin design, such as the equal environment assumption". My take on this is that the main result of the article is probably true, but the 50% figure is likely to be inflated.