As Sandy explained, the specific food used as an example is one of the middle quality foods, not the best and not the worst. The change in how the foods are rated has to do with the amount of consideration that foods with high plant protein get. Dogs use animal proteins better than plant proteins, so Dr Mike has started giving weight to the amount of plant protein vs. animal protein and how that affects the over all protein amount. So a food that is high in plant proteins, but not so high in animal proteins will score lower than a food that is high in animal proteins, even if the over all protein is slightly higher. He is only applying the new method of rating as he updates each review.
