Probably worth identifying one very relevant passage from your link:
Protein supplies the body with something called amino acids. Amino acids are building blocks to help build and repair body tissue. Your muscles, organs, bones, skin and many of the hormones in the body are made from protein. As a secondary role protein can also provide energy for your body if “carbs” are not available for fuel. However, proteins do not generally provide glucose when digested, so they have minimal impact on your glucose levels. Carbs, Protein and Fats – Their Effect on Glucose Levels | Joslin Diabetes Center
While much is not known about food metabolism, what is stated here is pretty well established. It is not controversial.