And the kicker... that there is no difference between plant and animal protein because once the body breaks it down into amino acids it can not tell the difference between "plant" and "animal" proteins.

Absolutely true. The only difference between animal and plant protein is the composition of the protein, and the digestability of the protein. Consider the difference between feeding a ribeye steak vs cooked whole kernel corn meal to a dog. Most likely the steak will have all "essential" amino acids contained in the protein. Where an "essential" amino acid is one that can be altered by the host body to produce other amino acids lacking in the diet. The proteins are readily available to the enzymes to break down into the amino acids. With corn the starch-cellulose or cell wall has to be broken down first, before the proteins can be accessed inside the corn cell and cleaved. The second difference is that corn lacks lysine and tryptophan which are "essential" amino acids. Although if not already available there are strains of corn being genetically engineered that will produce lysine. The lack of lysine has always been a problem for 3rd world human populations that rely on corn.

Thus the difference between pure meat protein and corn to a dog's biochemistry in regards to its protein or amino acid needs: Longer digestability required for corn, and a strick corn diet may lack lysine and tryptophan. But as you were taught a leucine amino acid molecule from corn is identical to a leucine amino acid from meat.

The commercial dog foods get around the all corn diet problem by doing the obvious - the dog food is not all corn. The degree that it does not contain grains basically determines the amount of total protein/fat vs carbohydrate in the diet. For the dog with kidney problems its dog food will have more grains since the total protein content is lower, while the carbohydrate content is higher. But again although a larger part of the low protein dog food will have corn and other grains in it, there will still be enough meat sources added to provide all of the "essential" amino acids.

Be prepared to be lectured about the wonders of a barf diet as being natural, or how a wolf is a meat eater blah blah blah. It's like religion. But as you have learned and will hopefully explore more education on your own, the perception of human taste buds does not reflect the reality of canine nutrition.