So short answer, yes you are are out of compliance if those are the only parts you have with a Benelli C-stock(even if it does not collapse). You will need a total of 4 compliant parts if you have a "C-stock".
You kinda have to remember that with 922R it's not about function, but more with number of foreign parts. If your stock and pistol grip are 2 pieces then it is a 2 part count. If you have a fixed stock with a pistol grip as one piece, then it's a 1 part count.
Now with CA, a collapsible stock on any auto shotgun is no bueno (Born and raised CA so I'm not making this up). That is a state law, where 922R is a NFA (federal) law. That's why its confusing, you in CA have to comply with harsher state laws on top of federal laws.