My point is that they far over-prioritized fuel economy. If you actually drive like that you will be spending a lot more time changing gears than necessary, and that almost any acceleration will require a downshift. I wouldn't recommend trying to stretch the gas mileage in the snow, for example, since you might need power to recover if you start to slide.
Overusing clutch is not such a big problem, but that it leads the driver to keep low rpm. Especially diesel engine is sensitive to that and can be damaged.
