Maybe it only relates to the parameters used for certification testing, that is to say weights below a certain figure were never used so that weight then becomes the lower limit. As we know most Boeing A/C use FL200 as the maximum flap operating height, I can only guess that the aerodynamics were never investigated at higher levels , so that became a certification limit.
As flight test programmes are expensive and time consuming to carry out, the manufacturer would normally only try to provide a certification envelope that covers 99.9% of normal airline ops requirements.