I have never heard of that and wonder how you know it to be factual?

No offence intended, I have a PB Rottweiler and have had dogs from about age 8, am past 70 now. I have found the old, farmbred Rough Colllies, could eat anything, but, my Rotts, for 30+ years, my absolute favourite breed, tend to have very sensitive guts.

My boy aged 9.5 now eats largely stewing beef and high quality wieners as treats, I don't like kibble and he gets a lot of meat scraps from our food, often eats MY meat by looking at me with a certain look and also mashed veggies, no spuds, pasta or bread stuff.

Looks great, no white muzzle and not much joint stiffness, a major issue with a Rottie.