You're talking about the basic function of protein or essential amino acids in diet and its role in overall body tissue maintenance.
But your topic is about taking protein in excess or going beyond the limit and exceeding the quantity sufficient to maintain the body's tissues. Ironically, the article you linked used subjects that are involved in resistance training where the goal is usually to increase muscle size and strength.
Furthermore, the article clearly states involving yourself in serious physical training in order to take advantage of excess protein in diet.
For sedentary individuals or only do little physical activity, high protein diets
may cause more harm than good (noting I used the word "
may" which means not with certainty):
Although high-protein diets continue to be popular for weight loss and type 2 diabetes, evidence suggests that worsening renal function may occur in individuals with—and perhaps without—impaired kidney function. High dietary protein intake ...
www.ncbi.nlm.nih.gov