Just watched the interviews, some interesting comments from Porte about the team instructions.
I wonder if it shows who Porte considers to be his main contender? He was more concerned about working with Froome to gain time over Contador than sitting on and beating Froome in the sprint to get bonus seconds over him. Or maybe he thought he could do both?
I think the team instructions not to work with Froome would have been the right choice. I guess they had the advantage of seeing that Contador was not coming back whereas Porte wanted to make sure he stayed in front and didnt waste the effort of going with Froome's attack. That's the whole point of having the DS there though!