Yes it's the same for the Nations Cup.
There was a time back in GTSport when it was your best result of the day that counted. People didn't like it though as it favoured those who could put in the time of racing all the slots with no risk to their points. There were also instances of people getting a high score in an early slot and then deliberately taking out their close rivals in later slots stopping them from getting decent points (it was rare, but it happened).
The risk vs reward approach of "do I risk these points and race again" I think is the better method.