Not eggs, but prey. They use this movement to break its bones and kill it.

It’s a sirirema if I’m not mistaken. There are a bunch of them in the country side of where I live (Brazilian Cerrado). They are absolutely fantastic animals

I assume the bird’s knowledge is inarticulate and all it knows is that it’s very satisfying to slam the ball on the concrete.

Ayup. These birds make the same movement with snakes and other animals to break all their bones.