my point was not clear but comparable.LOL my chickens also eat chicken... I use whatever meats I can get on sale, grind it all together (chicken bone as well) and freeze it in 1/2 pound meatballs for the dog's consumption primarily, but the chickens also get it now and then. the primary meat in these is venison, with some pork, beef, always some organ meats and then probably 1/4 bone-in raw chicken... they love it. I summer I can hang a meatball in a pen and they go to town tearing it apart.
The pork you are getting is probably the slaughter house stuff that we humans dont consume a proportional share of - liver, kidneys, intestines, brains and such, with a bit of meat. Its all boiled and then dried - much the same as fish meal.
I like my birds getting some non-vegetarian protein to ensure they get the amino acids they need - but I am not fussed what animal it comes from. I use fish meal the feeds I make. If chicken meal was cheaper, I would pick it without guilt.