They look 'tight' and are leather. The premium leather seats are mostly wrinkled and looser. Probably why Tesla has now switched to all Vegan faux leather. New seats also have adjustable headrests, Next Gen did not.
I don't think the premium seats were available in 2015. Only the next generation or the original Tesla seats. The original Tesla seats had vertical stitching in both the back and the seat cushion. Easy to distinguish these from the NG with horizontal stitching.