The salesman felt the combination of the sport package, with its speed rated tires, and the 4matic system might be at odds with each other. I figure, if MB is offering this combination, it must be fine.
I have never hear such a ridiculous statement. What does "at odds" mean? Ask him to explain the S500 4-matic with the Sport package, or the ML55AMG with permanent 4WD and sticky high performance Dunlop S9000 tires. They even offer the E55AMG 4matic in Europe.
The combination is indeed fine, but keep in mind that you will have to go to at least all-season tires in the winter months. You might want to consider getting your dealer to swap the Michelin Pilot Sport tires to the Michelin Pilot Sport A/S (All-season) tires when the car arrives. That way, you have all-seasons at least.
It is more likely that your salesguy knows that this combination will be rarer and take longer to arrive, and he wishes to sell you a car that is already in stock or enroute, rather than get one built to your specifications. [8)]