If by scale you mean the DOF scale printed on the lens barrel, then its highly dependent on the tolerances of the camera mount, adapter, and lens mount. The tolerances are not so important once the focusing is determined by examining the image through the lens rather than through the positioning of the focusing helicoid. Even PDAF DSLRs sometimes need to be "adjusted" at times. CDAF cameras which rely on contrast information through the lens is in more tolerant due to this and is often seen as an advantage. By looking through the viewfinder to focus, you are essentially doing the same thing as CDAF systems with your eye.... you are determining focus through information (in part contrast of sharp edges) through the lens using your eyes.
The rangefinders cameras are manufactured to very high tolerances (which contributes to cost) in order to obtain focus accurately. This is due to the fact that focus is obtained via position of the focus helicoid. If you look on Leica rangefinders, you will see a spring loaded arm with a roller. That mechanism engages M-mount lenses to relay helicoid position to the rangefinder mechanism which in turns determines whether or not the focus patch is lined up. Some more critical photographers will go as far as send a camera + lens into the manufacturer to have them "married" ie.... adjust the rangefinder exactly to the lens.
Whenever I use my rangefinder lenses adapted to any other system (MFT and A7), I always rely focusing by looking through the lens (again.. different experience from shooting a rangefinder). Even focusing out to infinity, I will still rely on looking inside the viewfinder..... many adapters will allow the lens to focus past or before infinity.
