Perhaps from the customers/buyers of the MM may have suggested it and maybe MM considered it a reasonable item to produce. MM buyers dont contemplate a W221 because its cheaper... They buy MM's for all the amenities and class of being a MM. Anyways this is just an article. It is what it is...

Again dont roll the average buyers mentallity as if every buyer had MM money to begin with. MM buyers are in a FAR different class.... They have thier preferences and would not contemplate a S550, because its cheaper.... These are two different buyers and two different cars.