I'll make it quick and simple. First, I don't believe that the cracks are due to settling, especially if the crack is superficial. Second, if your friend is looking to finish the floor, I wouldn't worry about the crack, because it will never be seen. No matter how much preparation work is put into concrete, it will crack due to its nature of contracting during curing. That is why control cuts are added to a large slab. It's the same reason why grooves are added to sidewalks. Tell your friend not to worry, it'll likely be fine.