Are you serious? I will not agree to disagree, LOL. It is fact. Maybe you are not understanding what I am saying?
Here is your shape - the work plane is the arrows I have drawn. That is the 2d workplane. The purple line is the edge and is 2d on that work plane, circled in red.
Profiles are 2d, shapes on a flat plane. They have an X&Y coordinate and can be all kinds of curvy, but they are still 2d. If you adjust the profile of a wall, it is still a 2d shape, in elevation. If you look at your section through the cylinder. It's still on a 2d plane, it's actually a section plane. Almost everything in Revit is extruded from profiles, or 2d extruded into the Z axis which makes the object 3d. Faces are flat, most edges are 2d. Here is a graphic -
The only objects that cannot be described with a number of 2d faces are the objects that have curved faces. I could place a 2d workplane on any one of those faces, except curved, and draw a 2d profile. Or slice through any of those objects and the edge created is a 2d profile. Is that a little more clear? What I want to do is draw a completely 3d line, like you showed with the 5-Pt. Adaptive Point Family, and use it as a path to sweep my profile. I'm looking for the easiest way to create that line or edge.
Regards Peter.