if you are focusing with a tripod and everything is fine
and hand held it is slightly out of focus, at f4, it seems that
you have moved, or your subject has moved, ( or both ) so your focus
is a little off ... this is the same problem a lot of people have with LF ...
especially when one has to focus, stop lens down, insert film, pull dark slide
and make the exposure ( and the camera is usually on a tripod ) ...
maybe rollei suggests focusing on the nose to compensate for people moving forward
just a tiny bit, when someone is taking their portrait ...