The minimum twist mode is important because it allows creating normals without sudden changes in direction. The disadvantage of minimum twist normals is that the normals depend on all control points. So changing one control point can change the normals everywhere. The computed normals do not match the existing code exactly, although they do match quite well on non-cyclic and on some cyclic curves. The existing code isn't bug free anyway as can be seen in the demo file which shows a bad artifact of the old code that is not in the new version (afaik).