my guess is because it came from a HLE since not all of them carry more than F cars.. If the HLE is in a high profile area they will have better than F cars. I have received a few Prestige cars while booking a F from several HLEs only because they normally have a few in their fleet. My assumption is an HLE will give you the best car they have as a Platinum. With large airport locations getting more than a luxury is purely based on relationship/frequency and of course availability since they can see up to 15 platinums a day.