I can't get as powerful a swing when launching from the experiment position alone. I'd have to surmise that either rotation begins before heel plant or that the weight shift 'rolls-over' into rotation, transitioning through the heel plant in a way that cannot be attained by mere explosive muscular exertion as in the experiment.
"Glide", "swoosh", "swoop", "Gravity is energy" type of descriptors come to mind.