Anyone know why the wheelbase is different for the coupe version? In fact the entire frame is seemingly different as a result of this. It kind of flies in the face of how cars are moving towards commonality. There has to be a pretty convincing reason for MB to do this since it would stand to reason that using the same frame of the SUV would greatly simplify logistics and production.

 

The "commonality" of cars these days is essentially the A Pillar forward, maintaining the pedal to steering wheel and firewall distances and most elements of the front clip. That standardizes design and parts, but mostly assembly line procedures, where installation of wiring, dash etc is similar.

VW Group started this practice about 20 years ago with their MQA, MQB, MQE etc. chassis, on which they build everything from the Lambo Uris to Seat sedans. Saves on Robots and procedures on the assembly line.