Good point. Case in point: Cancellara's masterful descent here [1]. It's one of the least aerodynamic (I'm certain I can get more aero on a straight descent), but I would get dropped hard on the first curve. Especially on curvy descents, it's all about taking the right line at the right speed. But I am happy to see Froome's position is not even that aero. It certainly looked unstable.