I think it depends on what they recognize as food, which is crucial when the bird is being weaned. When Alex was still being fed, I put him in front of the pellet bowl, and he would stick his face into the pellets (literally). Now, he eats more pellets than seeds. I see him eat seeds every once in a while, but he acts like he doesn't like them.
and he knows they're food. I guess he's just weird.