Your chickens are definitely on a different diet than factory farmed ones, haha

Well it's both. Many animals can eat a very wide diverse mixture of foods. Like cows, they can eat grass, but also hay or grains. So it could be that you're both right.

I'm not an expert though.

Chickens were classically considered food for the rich because they eat grain. They are an exception among livestock in that regard. Talk about animal husbandry.