I did take that course recently (a very good one). The lesson is, indeed, about how Blender stretches/reshapes things when it unwraps, but it basically assumes that everything is stretchy. Typically what you want is to get lots of faces to fit / pack / cover a surface without distorting too much. Blender uses various rules to try to help you. “Preserve shape” seems to be irrelevant for most texturing – just my special cases I guess.
