Sorry, I should have been more descriptive. If you fit an arc between two points without a signed centre, it can go two different paths and still be a G2 clockwise or G3 counterclockwise. One path is a minor arc, the shorter of the two, and the other is the major, the longer path of the two. One will blend in smoothly with the rest of the geometry, and the other will be abrupt, but the control will still agree with it. An Accurite CNC mill I use has a soft key to let you choose between the two. Mach turn seems to always go for the major, the longer arc if you use an R value instead of a signed centre point.