no, it’s a different one. Rhino’s built-in command TweenCurves was the inspiration to write my own, so I called mine TweenCurves2 and published it in the “Tweener” package. Its purpose is the same - to tween curves - but it takes a very different approach at doing that. Feel free to try it out. To do that, type _PackageManager in the Rhino command line, search for “Tweener”, click install, restart Rhino, select two closed curves like yours - but they have to be in the XY plane, one contained in the other - and call the command “TweenCurves2”. It gives you lines that would be the level curves of a different way to look at your geometric problem. You would have to go up in the third direction, but you would have a potential workaround for the sweeping procedure.
Don’t hesitate to drop me a line, whether it worked or not!
The output should look like this, indicating how the undercut is avoided (which might or might not be what you wanted?)