That level of acidity is enough to handle soybeans and soy products by breaking them down into their basic components. Eat soy protein and it is easily broken down into a very rich amino acid broth which nourishes and feeds your cells. If you eat 50 grams of soy protein you will utilize all of those amino acids as fuel for your body cells and functions. Protein in milk presents a different set of circumstances. Protein in milk is exactly the same as protein in hamburger.
Milk is liquid meat.
However, the body treats that protein differently. In meat, the proteins would be broken down and provide fuel for the body. In milk, these same proteins are not broken down. They survive, intact. In doing so, these proteins are circulated in the blood to all cells.