This doesn't apply exactly to this question, but I had an early check-in once at the Tampa Westshore Marriott and since my room wasn't ready, the clerk told me to go to the restaurant and show my platinum card to have breakfast. This was on the weekend when the lounge was closed. I suppose if it had been during the week, I could have taken my card to the lounge and probably gotten in without a hassle. That's an assumption of course, but the way they handled my situation led me to believe this.