Taylor confused the logical proposition that planning and doing are distinct functions with the empirical claim that these two functions are always best performed by two distinct classes of people endowed with distinct educational pedigrees, clothing styles, and patterns of speech. The one is nonfalsifiable; the other is simply false. Cutting up your food and eating it are distinct functions too, but it is not the case that they are always best performed by two different people. In manufacturing businesses, separateing planner from doers sometimes makes sense; but, as Japanese carmakers proved to the dismay of their American rivals, getting the doers involved in the planning can result in higher-quality products and lower costs.
— Matthew Stewart, “The Management Myth”, p 55-56
I see a lesson here for software product managers: if you get the developers involved in the product planning process, you may end up with higher-quality products. The developers are not mere tools that serve the ends of your planning process; they can be very useful in helping you devise and define that product, espeically since they are the ones that have to actually build the thing.