Great camera, isn't it? I get enlargements to 16x20 from that that rival my 4x5 negatives.
Think of rangefinder as focusing with your eyes. Looking at the door handle of a car across the street and down the block, you can't really judge distance from that to the person walking on the other side of the car. Your eyes are too close together. But with the short DOF of a 210 or 300 lens, one would be in focus and other wouldn't. And you wouldn't know which. And so it is with a RF camera, whose "eyes" are even closer together than yours.