Diffs ( non brand specific ) with a wide range of ratios have always moved the ring gear mounting surface but not for every ratio like MB. An example of a USA unit would be 3.27 and smaller number is one carrier and 3.45 and larger another.

In order to accomplish this wide range, the ring gear must be thicker as the numbers get larger. This leads to more rotating mass / material used. MB kept the ring gear thickness the same across all ratios and just moved the flange. We also don't know if there was a thickness limitation in their gear cutting machines when this was instituted.

While this causes issues for the microscopic number of people that swap ratios, it works out better for the 99.99999% that drive the car and not change things.