This area, as I mentioned, is high elevation in the Rockies; close to the tree line. They get maybe a 5 month growing season at best (June to end of Sept). Undistrubed soils are thin (30 cm profiles tops) and rocky.

In comparison, in good soils around here, I'd expect 10 year old trees to be 2-3 m tall; thus, given the challenging growing conditions and the complete lack of soil, I think this is pretty good. Should their reclamation prescription use not use soil? No. I say, if it's there, use it. However, mines are almost always short on material due to their inherent changes in topography (which creates more surface area to reclaim) so I think in areas you're short, this is viable and comparable, given that across the valley, on an undisturbed mountain the trees probably look similar at the same age.

why mound like that

Rough mounding is used for three reasons:

1. Slow water movement, and reduce erosion
2. improve water retention on the slope for the plants
3. Create a divers micro-topography that results in more microsites for a wide variety of plants to grow. Some do good on the tops of hummocks, while the the more shade and thirstier spp. do well in the hollows.