It is a bit of a challenge getting curvature continuity. As you can see with the blended object in the post above, the result is not always what you would expect.

Also, in software that supports extensive surface continuity, like Solidworks, that I use, a lot of times SW will refuse to create the surface, just reporting that the continuity requested cannot be achieved. This often happens when patching a squarish hole. It is often because the bounding surfaces are not themselves surface continuous at the same degree, and the patch will fail at the corners, because of conflicting curvature. Where it does succeed, the surface can be extremely distorted and not at all what you want.

It will be quite a big job for Michael to build this in to V3.