the restrictions for use of collapsible lenses refer to the Leica M 5 and the Leica CL only. These body have the measuring cell on a swinging arm which swings into the space between the lens and the shutter. If the lens is collapsed and you try to measure the ligt, the arm could be damaged. In the M 6 and upward the collapsed lens (or a Super Abgulon or first type of 28 mm) only shades the exposure measuring cell.