Is this subsoil that you're considering light leveling with? Or are you leveling a yard by raising it a good few inches/feet. If light leveling then no, it'll be more trouble than it's worth. But it may be ideal subsoil for raising up areas that need a good compactable base.
Edit: looking closer at your pics, seeing the slab, and I'm assuming this is the excavation soil from where the slab was dug down. That's approx 6" of dirt, which in most cases would be categorized as topsoil. If so fee free to level w it, being mindful to collect as much of the gravel as possible.