There are many reasons, from what I got from the article, for the V-diet being the way it was.
Beyond what was already listed WRT Casein, Protein Amounts, etc.
It was designed to also be think-free. Once you hit the calculations you knew what you were having every meal and it was very easy to set it up.
It was also cheap and allowed you to get all foods out of your cabinets except for the shakes you had. Plus, Metabolic Drive shakes have some extra vitamins that just eating plain tuna wouldn't have.