I am having the same problem. You say to include the faces, but in the tutorial you have vertex select on, hit E and drag over without pressing anything else. Is there a setting that would cause this not to happen?
Because I do the same and press Y to go along the axis and the mesh goes with the curvature but the vertices do not:
https://jake-bigrookgames.tinytake.com/tt/MzkzNTQzNl8xMjA3NzUzMA
I realize after scaling it is essentially the same result, I am just a little uncomfortable not understanding why it behaved differently.
