The mystery of pistachios.

I often find pistachio nuts out of the shells. In the same bag, I sometimes find pistachio shells that are empty inside with their slits just slightly more open than the normal ones but not open enough for the nuts to escape…

My theories:
I. These shell didn’t have nuts ever. The naked nuts are unrelated to the empty shells.
II The nuts were very very small and they could fall out.
III. The nuts were very very flexible and when nobody was watching them, they twisted their bodies around like gymnists and sqeezed themselves out.

I hope it’s the third theory.