Yeah, that's weird. If a chicken is truly "cage-free" or "free range," they will definitely eat bugs, worms, etc. I had chickens for many years as a kid and learned that chickens will pretty much eat anything. We used them as our natural garbage disposals - feeding them all kinds of kitchen scraps that included meat, veg, fruit, etc. And we had wonderful, tasty homegrown eggs for many years that had beautiful dark yellow yolks.
And we had ducks for quite a few years too. I learned from a young age that a duck's favorite treat are garden slugs. And we had some really tasty duck eggs!