I don’t think that cataclysm differentiates between carpeted floor, grass, and rock, cement, or lenolium as far as comfort goes. Grass or carpet is already miles more comfortable than anything you could make with paper, although I can tell you from experience that a few newspapers or cardboard boxes make a world of difference if you have to sleep on a truly hard surface.
So: realistic, yes, but not quantitatively representable at Cataclysm’s level of detail.