Of course Ford's original "design intent" for the E350/E450 series was for vans - with their wheelbases way less than that on motorhomes. With these short van wheelbases, turning radius is adequate.
For the case of our 24 foot Class C with it's short-for-motorhomes 158 inch wheelbase (which is still much longer than that on a stock van) on an E450 chassis, we can almost do a single point U-turn on most residential streets if there are no cars parked along the curbs where we turn around.
I suspect that the design intent of the Mercedes chassis was the same. But since the Mercedes chassis can't handle large/long Class B+/Class C motorhomes anyway, whatever turning radius the Mercedes has will seem adequate for the short motorhomes able to be built on it.
