There's also a huge difference between what is BAD for them and what is just not as good as another thing. I'd absolutely toss in scrap pizza crust even though it might not be especially healthful. And when I made shredded beef the other day, I split the pile of spicy fat between the cat, dog, and chickens so none of them got too much and they all horked it down. But, I didn't put in some cucumber peels because I peeled the thing in the first place because the peel was tough and waxed.
There are also a few questionable things on some no-no lists. Citrus, for example. I fed the chickens an overripe orange yesterday and they went bonkers for it. They're running around just fine today so I'm pretty sure it's going to be OK. But there are some folks who are adamant that citrus is not good for chickens.