the 6-bit coding doesn't have anything to do with the frameline selection, that has to do with the physical lens mount. the mounts differ very slightly (24-35, 50-75, 28-90), and they will physically shift the frame selector to adjust for the framelines (as dictated by the lens mount).
the 6-bit coding is read by the m8 via the sensor at the bottom right of the camera mount. if you have enabled lens detection from your menu, and assuming your lens is coded, the sensor would read the binary (black and white... well, actually only the black) to identify the lens being used. this is for writing it into your exif data, as well as auto jpeg adjustments.
e.g. even though all leica 50mm lenses would choose the 50mm framelines, the 6-bit coding can help distinguish among the 50trielmarit, 50summilux, 50notilux, 50summicron, 50summarit, etc.