We avoid gutloading with dog/cat food because of the ANIMAL protein, not because it just has generally higher protein content. Animal protein plus the added vitamins geared toward larger animals and digestive enzymes which are meant to help mammals, just don't bode well for either the insects or the reptiles that eat them. It's not normal food for them at all.
I don't know who deemed it suddenly ok to gutload with dog/cat food. It makes no sense when you look at it logically, it's just a quick and cheap fix to feed a huge colony.