Some know more than others.
Every once in a while, a FA will give me special service because they know I'm a plat. Not on domestic flights, as I'm in 1st 99% of the time anyway, but on international flights in coach, they must have some kind of manifest that tells them a little about who's whom. I have had a FA on her own retrieve some red wine from the business class section (instead of simply giving me the coach stuff), and another did something else along those lines years ago. I don't expect it at all, so it's always a pleasant surprise when it happens.