You can easily demonstrate the effect that Bruce referred to by taking a business card out of your wallet and letting it fall to the floor. The CG is in the center but the CL as an airfoil is towards whichever edge happens to be the leading edge. This results in a continuous tumbling as the card falls. When I was a kid, throwing a yardstick as high in the air as I could and watching it spin at a high speed as it floated to the ground provided endless amusement.