The point is that the 'gimmick' in question is meant not only to tell you whether or not you slept well, but also to tell you why you didn't sleep well.
I don't know how well this works in practice, but I know that's the primary purpose of similar functionality in Sleep Number mattresses ("You didn't seem to sleep well; you should bump your number up to 63 and raise the back about 2 degrees more"), and I figure it would be the same with a smartwatch counterpart (though probably with less precision; it can detect the tossing and turning, but probably can't detect pressure points the way a smartmattress theoretically can).
I don't know how well this works in practice, but I know that's the primary purpose of similar functionality in Sleep Number mattresses ("You didn't seem to sleep well; you should bump your number up to 63 and raise the back about 2 degrees more"), and I figure it would be the same with a smartwatch counterpart (though probably with less precision; it can detect the tossing and turning, but probably can't detect pressure points the way a smartmattress theoretically can).