It's not just chainrings that can be out of round. I have at least one all-city rear sprocket that isn't radially true. I also have a mavic ellipse rear wheel where one side is unusable because the sprocket mounting threads are so far out out of being radially true. I also prefer a loose set up since it takes the load off the hub and BB bearings and spins faster. It's also more tolerant of less than smooth pedaling.