I want to create a sheet metal part consisting of two concentric cylinders using sweep feature like this:

But I don't know how to flatten it. If the transition between cylinders is vertical, the flatten will fail.

If I set the transition as conical, it can be flattened but the result looks weird.

Actually, I also don't understand the official example of this feature.

2019 SOLIDWORKS Help - Swept Flanges for Conical and Cylindrical Bodies 

I think the flattened sheet should look like the following sketch, as the radius and arc length of the upper and lower side of the cylinder should be the same. Is it because it includes the deformation of the metal?

So how to flatten a sweep flange properly? Or is there any other method to create and flatten two concentric cylinders in sheet metal? Thanks