What specific limitation related to its gizzard structure means the parrot likely cannot process hard seeds?

Answer

It has a poorly developed, weak, and narrow gizzard

Research suggests the species has a poorly developed, weak, and narrow gizzard, which correlates with an apparent inability to process hard seeds found within fruits.

What specific limitation related to its gizzard structure means the parrot likely cannot process hard seeds?
foodbirdParrotPesquet