Curious..
Here, try this (it is not a solution to the problem but interesting none the less.
Sample models of what I have discussed here are at
Next make another part and draw a circle with a diameter to match the length on the line in part one on the front plane and create a 90 degree helix at the same distance the planes are separated in part one. do this again and crate another helix but at 180 degrees out from the other at the same rotation (counter clockwise if that is what you used). Next create 2 3d sketches based on one of the helixs'. and another for the other helix (sheet metal will not loft off of a helix) and then loft a sheet metal part off the 2 3d sketches and look at the flat pattern. it is perfectly square....
I wonder if on some of my lofted bends in the past could have been much simpler if I had used a different modeling technique? This non conformity for the flat pattern is most likely the reason we cant add anything to a lofted sheet metal part as given it is the same part but two possible flat patterns then there is some problems with the lofting algorithm.
Ben