In a perfect world you ought to incorporate non-associated cushions on inner layers. It helps amid the plating procedure to have extra copper to plate to down the barrel of the opening. The annular rings don’t need to be as enthusiastic about the inside layers as there are no tracks prompting them and you won’t bind them.
PCB fabricators can adapt without (they plate 2-layer sheets alright) however can be reliant on the gap diameter:depth proportion.