By using the AFM figures you do not get the shortest possible ladding roll. What you get is an approach that will enable the ‘average pilot’ to most consistently reproduce the landing distance tabulated and also have a safe margin for a go around. If you are an Alaskan bush pilot flying fishermen onto sand bars you will probably have a different set of figures that you can make work due to your greater experience and familiarity with that type of operation. But not many flight schools are teaching Alaskan bush pilots. The average student does not even come with the ability of the average pilot.