Within 30km of the finish, I think, they are not allowed to collect fodder and gargle from the team car; imagine the potential carnage.
There are neutral motorbikes handing out drinkies to those in need.
Okay - so the rule is to stop team cars from hanging near the front and clogging up the race? That's sensible on narrow alpine climbs; but if you have a domestique that is willing and able to go back to safe distance and schlepp up some bevs, then what's the harm?
Mind you, I don't think Porte had to go back far yesterday, so the car couldn't have been far away.