You might want to check kbb.com, sounds like Edmunds has some errors.
1. Exterior Sport Appearance Package is optional on both the V6 Deluxe and V6 Premium. It is not included on the Premium.
2. According to the Dealer Order guide, you can only order the Leather Sport Buckets (order code K) on the V6 Deluxe & V6 Premium if you also order both the Interior Upgrade Package (code 18G) and the Interior Accent Package (code 68R) and Dark Charcoal interior (code KR). To me this says that you will get the red seat inserts, that is the sport buckets are the red seats.
If all you want is leather seats and not the IUP, ICAP and red seats, you can order the leather buckets, code J. (V6 Premium only)
But I have to say that I'm not quite sure I understand the dealer order guide. In one place it says that "Leather Sport Buckets" are the seats with the red inserts. In 2 other places it shows them being standard on the GT Premium, which I don't think is the case. I'd guess that's an error in the guide that the regular leather seats, code J are the standard seats on the GT Premium.