Thomas
If you want to plot Sections of a Vertical Design that follows an Alignment then you can add the surface that it created to a Corridor and still create Cross Sections.
No-one has said that Vertical Design is a replacement for Corridor Modeling. Vertical Design is primarily for Site Modeling although it has many potential applications in Highways work as well. For me Vertical Design is an additional set of modeling tools that can rapidly model complex scenarios and carry out value engineering to resolve design issues on a project. However creating Profiles and Sections still require an alignment to cut against and vertical design doesn't replace the Alignment Editor or the need for alignments in the process of creating Sections and Profiles.
I agree that converting a Linestring into an alignment is still one step and adding surfaces to a Corridor a second step in the process of creating section output, but those steps really do not take a long time, and you can in fact add surfaces to a Corridor as Reference Surfaces instead of as Surface Instructions if all you want to do is plot the Section Lines (and not the volumes between surfaces), and the section creation process will still work.
Alan