Some neighbors used to have a VW bus with a personalized license plate that said, "LOAFIE." A box with rounded corners is as valid a shape as any, but there are different connotations. What's fun for a cheap van undermines the intent of a status symbol.
The Mercedes I saw looked like most of their other SUVs in the US. Most look like loaves of bread, while there are a few G-wagens that are high crisp boxes.
There are a few possibilities I can think of for this one.
1. A future drivetrain for Mercedes or a related company is being tested. Underneath, it could be a 2017 Toureg, Cayenne or whatever.
2. This is the future of Mercedes styling. The iPhone is inspired by German design, and this SUV anticipates the advent of a fat iPhone, a loaPhone, that also doubles as a server.
3. It's an older prototype. The driving company has to return it soon, but they use it to run errands in the meantime.