If you create a surface then x-sections of that surface does the surface update if you edit the surface lines in the sections?
How would it determine the correct modification to your model that would create the change you want in the section?
Editing corridor x-sections is a different story, because editing the x-section alters the corridor definition for that station. Then the corridor surface is generated from the corridor definition.
But when we start talking about sample lines across surfaces, there are an infinite number of changes that could be applied to the surface definition in order to create the desired change along the sample line.