I think people were worried about protein not being stored. Broken to glucose(that can stored) or fat(triglycerides mostly). The breakdown is complex and the referred article lists high as 1.5 / kg so 220 lb man would be taking in over 300g…pretty high. The breakdown of the ammonia is done by liver mostly in the process of turning this to urea. Any breakdown and yes kidneys can’t really get all the nitrogen waste(ammonium ion) filtered. What about 450g of protein , diuretics, AAS…maybe becomes to much to handle. But I’m just playing devils advocate.