I totally understand the balancing act that MB has to go through. Provide enough service to make the car last awhile/not so much that the car stays in the shop all the time. Most people don't keep their car near as long, or put near as many miles on it. So the FSS probably works out fine for MOST Benz owners. I'm in no way a typical owner. I drive 60,000 miles/year or so. I keep it and drive it until the wheels fall off. Therefore, synthetic oil, changed hot and often will most likely take my car further than the typically maintained car. I still say it won't hurt unless I leave out the plug, or forget to pour in the new oil.
With that said, I'll change my oil often and keep an eye on everything I can when I change it. I doubt that I'll get 380,000 out of the original engine, like my 240D did, but whatever it turns out to be, I expect that it will be longer than typical.
Only time will tell,
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in