Andrew, great points throughout. I'd like to especially point out what you finished with, though.
When runners do not have a functional grasp of the physiological concepts, they often do things like grab components from four different styles of training and cobble them together in a Frankensteinian fashion without an idea of how those components work together or how they might be counterproductive to each other.
I do think it's important to take ideas from various sources as I'm very sure you also do. I also don't think it takes a degree in exercise physiology to know how to put the pieces of the puzzle together, again I'm sure you would agree. Still, as you point out, I see people all the time piecing together training plans from various sources in a way that leaves huge holes in their plans.