The product will have an earthing terminal if it satisfies the following 2 conditions:
1 - condition 1: if the product (RCBO or RCCB) is voltage dependent.
2 - condition 2: if the neutral conductor is not protected.
For example:
1 Pole RCBO (A9D34806) has this earthing terminal to provide a referential voltage in case of disconnected neutral wire on the terminal block, even if the neutral wire is not connected on the CB, the associated load can be supplied. Thanks to the earthing connection, the CB is supplied and protect the load.
2 Poles RCBO (A9D11210) product does not need the earthing terminal block because the load is never supplied if the neutral conductor is disconnected