Pie throwing is what you would get if you took Marshall’s guys and asked them not to pronate as they drive the ball toward home plate. Ball facing skyward at the back of the driveline (as if they were balancing a pie plate on the palm and fingers). In my experience players who are ‘pie throwers’ have learned to throw this way because it eliminates much of their shoulder discomfort. They have eliminated late forearm turnover. For guys who throw naturally like this is would be substantially easier to teach them Marshall mechanics because they do not have as many flaws to ‘unlearn.’
You have noted several times that you ‘believe’ it is possible to combine what Dr. Marshall is advocating with traditional mechanics. This subject is one of the specific reasons your ‘belief’ can never see daylight at a remotely competent level.
Heaven forbid some folks take this to mean that Marshall’s students are pie throwers. Far from it.