When I did my first oil change, it did not seem to change the mileage to the first FSS A Service.
They are already learning about the effects of the FSS. What they already learned is that if you follow the FSS recommendation with Dino oil, the engines are getting nasty inside. That's why about a year or so ago, MB started providing Mobil One for their free oil changes. Before that I was planning on taking my own Mobil One and leaving it with them for the change. Now I don't have to do that, they provide it.
Mobil One or not, I feel much better changing the oil twice as often as the FSS system says. Even Mobil One is cheap compared to one of these engines.
Have a great day,