Offset Surface

Q1: Offsetting a B-spline often gives a multi-segment spline. Offsetting a B-surface gives a "Offset" surface, which seems to have no poles as tested by Show Poles command. As fas as I know, only faces from Extrude of Revolve don't have poles. Can you give some clues on how to understand the surface type "Offset"?

 

 

Q2: I need only one edge (pink) of the new offset surface. Is it possible to create it without using Offset Surface or Thicken? (Note: Here is only a simplified example. The edge might be a 3-degee non-planar spline.)

 

 

Thanks!