The author mentions slopes but doesn't talk about afternoon versus morning shade, Boggy B.
There are advantages to afternoon shade. A couple hours of relief from a blazing hot, afternoon sun can be of benefit. Of course, there can be too much of a good thing.
Morning shade -- I don't like it. My smaller veggie garden has some very tall bushes on the east side. Other than that shade, that garden is pretty much in the full sun for the rest of the day. The rows run east-west so you can really see a difference as you get close to those tall bushes. Very close, and the plants just darn near peter out.
And yes, there are issues of roots but that's true in my Shady Corner; a triangle that begins to get shade about 10am. By noon, that patch of ground is pretty much in the shade for the rest of the day -- tall trees make sure of it. The trees allow some patchy sunlight thru and I know the plants appreciate that but there's not a great deal of it.
Reflected light? Yeah, I suppose. But, feel the energy in direct sunlight!! Blue sky north of a tall building can't match that. However, painting a northwall white is of some real benefit at this latitude where the sun swings so far into north sky, morning and evening.
Are greens worth growing? You bet! Lots of protein in green leaves! Leafy greens, leafy greens! How often do the nutritionists have to tell us??
I am curious about others' experience with potatoes in the shade . . . does that work? Seems like an early variety that would be ready to harvest in late July might take until September and be just fine . . . but, I'm only guessing.
Steve