Meh, it's a shortened warm down lap, IMO that would have been the time to ask if Rosberg wanted to, although that could be perceived as weakness, in the final laps his job was to focus on the task at hand. I'm not sure if/why he would be shocked that Hamilton came third, Hamilton pulled into the 3rd podium parking spot right in front of him, so unless there's a secret additional Merc driver out there Hamilton's position should have been clear.