Apple is seeding an initial beta of iOS 6.1.1 to developers. In notes for the release, Apple explains that the update is meant to fix problems with the Maps app in Japan. This includes several improvements to navigation, such as better pronunciation of road names, preference of highways over narrower roads, and warnings about toll routes.
More general tweaks for the country include labels for junctions, interchanges, onramps, offramps, and intersections, and indicators for transit station buildings, subway lines, and traffic lights; the freeway color has been changed to green, and icons have been updated for location categories including fire stations, hospitals, and post offices. Among some newly 3D-rendered buildings are Tokyo Station, the Imperial Palace, and the Tokyo Tower.
iOS 6.1 was only recently released to the public. Apple may have wanted to bake v6.1.1's changes into that release, but may have thought it was more important to get a global patch out fixing regional issues.