If that were true, no development or experimentation would be possible. A class can set whatever rules (or lack of them) it wants to regarding sails. If the class wants to approve a spinnaker that is shaped like an hourglass, so be it.

If a class decides to become an ISAF International or Recognized Class, then their class rules are kind of set in stone. If an ISAF class wants to make a change, they have to first vote on it as a class and then get approval from ISAF to make the change.

The RRS are the rules of racing, not of design and development.

If I am wrong about this, I will drop out of sailing and take up knitting.