S series, E series, X over...seems like a more reasonable explanation. It wouldn't be cruel since it's not at all clear what percentage of people would have bought the D had it been an option all along. Those who put AWD above other things are on the X list. There's a difference between "this car lacks ACC while all competitors have it" and "this lacks an AWD option and so do many competitors but I could buy the option on some competing vehicles."
Plus, it's hard to define "competing vehicles." It's doubtful that many people who drove $50K to $60K cars suddenly saw a Mercedes in that price range as a "must have" item, but it's true of Tesla owners. There are also Tesla owners who would have spent substantially more on other cars, but liked the MS better and consider it a bargain. I don't know of any other vehicle where people would consider whether to get it instead of a car half the price or instead of one twice the price.