"There is a reason diseased, condemned, and/or non-slaughtered animal material is illegal…it is dangerous to consume. "
This is the nub of the question. Who or what is in danger from eating substandard food? Just because food is not up to human safety standards does not make it unsuitable for animals. If you want to treat your fur baby like a child and feed it human grade food go ahead but then you will pay for it - your choice. The fact is that animals are quite capable of eating things that would make you or I very ill. I will speak of dogs as I know more about them.
A while ago my dog was putting on weight and I couldn’t work out why. The short story is he was supplementing his normal rations from a dead cow. He would vanish for half an hour, gorge his fill, come home, sleep and return to the carcase as often as possible. This went on for days until he was visibly gaining weight. I back tracked and found that he was in a revolving queue with other scavengers who were working through the carcass. You could smell it and hear it (blowflies) well before you could see it.
He cleaned out the rabbits on my property, leaving no mess behind whatsoever. They were not slaughtered in hygienic conditions but however he got hold hold of them. He happily ingested (and subsequently eliminated) all the tissue; meat, bones, fur, claws, I mean everything, there was hardly a speck of blood left when he was done. Cleanliness is next to godliness.
I mention this not because I think it is the right way to feed my dog but to show it is possible. I did not encourage this but I could not always prevent it either. He never showed any ill effects from his varied diet (including coprophagia). I did ensure that he was regularly dosed to deal with possible parasites because the alternative was he would have to live on a chain. [Note that prepared dog food cannot transmit such.]
Ok enough revolting stories, the point is it is quite reasonable to have two different standards for food preparation because you have two different sets of risks.