In fairness to Mr. Peterson I think we may be misinterpreting what he says. To qoute in full from Understanding Exposure (section on exposure meters page 125) he says: "In addition, I do recommend taking another exposure at - 2/3 stop when shooting most any subject, since this often improves contrast and the overall color saturation of a given scene. This comparison shot will allow you a comparison example so that you can decide later which of the two you prefer. Don't be surprised if you often pick the - 2/3 exposure."
Seems to me that he is offering a suggestion for many situations for one's digestion and comparison not an absolute rule for everything! Of course we may disagree with his suggestion