In order to have the same horizontal field of view as the Ricoh Gr (which is a 2:3 aspect ratio camera), you need a 13mm focal length on a Micro Four Thirds camera. So that’s the reason for the strange focal length.
This crop is from the very top of the 3:2 frame, close to the right corner, but not the extreme right corner.
The Ricoh GR is the sharpest camera/lens combination that I have, and therefore I was shocked to discover that the 12-40mm lens provides the same amount of sharpness as the Ricoh GR. Very impressive!