It sounds as if Mortensen's techniques are geared primarily for studio work where the photographer is in complete control of the lighting. Apparently he did lots of bracketing and then chose the best negative. If that is the case, then his method has very limited applications in the field. AA did not have a chance to bracket Moonrise Hernandez. In fact, he didn't even use an exposure meter, he couldn't find it!
As for the Zone System, proper application will encompass just about any lighting situation one will come across and allow the photographer the expand and contract contrast as the artist sees fit. Picker believed that exposing for the high values, not the highlights was the best way. Large parts of the subject would be placed on zones vii and viii such as clouds, snow, clapboard etc. Highlights are generally very small and will usually fall on zones ix and x.
His workshops required you to do a personal ASA test, and development tests for complete control of your materials. He also believed that it was best to place the exposure range of the subject as high as possible on the "S" curve of the film for maximum separation of tones, then print expressively.