Is it confirmed that the shot showing Ron/Chris running and Nic/Don with backpack is the location of the final mat?
I think it probably is and the reason why Chris and Rachel wear jackets when doing roadblcok is because that area is not the same place as the final mat, maybe they have to do the roadblock in some place and get the next clue to the finish line, so on the cab ride they take off their jackets.
And it is clear that the shot with Don, Ron and TK together is when they all wait for their teams to finish the roadblock, so you can tell that they are all there around the same time.