Where are these images? Were they taken at close distance? Different lenses behave differently as they are focused closer and their effective focal lengths change.
The V1 shoot 3:2 and the EP3 shoot 4:3 images, so a V1 image will have a wider horizontal FoV for the same equivalent FL (same diagonal FoV), but it sounds a bit strange that 10mm on V1 should have a much wider FoV than 12mm on EP3..
According to DPR, the V1 sensor is 13.2mm wide and the EP3's sensor is 17.3mm wide. So the V1's width is 13.2/10 or 1.3X the focal length and the Oly's width is 17.3/12 or 1.44X the focal length. So, if indeed the Nikon is wider something else is going on.
Doing some RAW comparisons might be worthwhile. DPR's preview of the V1 noted that the lens used was designed to correct distortion to a fairly high degree, so in-camera correction doesn't have much left to correct. This correction results in cropped images in JPEGs, so comparing RAW, uncorrected images from both cameras will show what their sensors actually see. If there's still a big difference, well . . . Oh, and the photos should be focused on very distant objects to eliminate the effects of focus breathing, if that's affecting the comparisons, since that can produce significantly shorter focal lengths than expected when the focus is closer to the camera.
