So I've just had a practice session, and it seems that my observations were correct. I set up the balls as diagramed, stickered-up the ball positions and shot each cue ball position several times. I hit every shot with a medium stroke speed as instructed in the book.
I did indeed, as predicted in my first post, find that I got the shallowest angle off of a 1:30 strike, heading toward position a with it.
A 4:30 shot as predicted headed more toward the e position.
12:00 strike headed toward position b.
3:00 headed more toward position c.
10:30, 9:00, 6:00 and 7:30 were pretty accurate.
Again, I just can't see why if a 6:00 shot comes off the cushion backward, and a 3:00 shot comes off pretty straight, then a 4:30 shot wouldn't come off somewhere inbetween, which in my experience, it does.