I am wondering if when your friend butchered he ruptured the bowels because I have not noticed a smell different than when you open up a package of chicken from the store. I've butchered quite a few chickens and the only smelly part would be if you accidentally cut into the bowels. However, maybe there was another determining factor for him that caused the smell.

It's honestly super easy to butcher chickens, especially if you skin them. :)