This is not actually the interface that is used on the Dragon. This is a docking mechanism, which allows autonomous connections between two spacecraft. The Dragon uses the Common Berthing Mechanism (CBM) which requires assistance from a manipulator arm to mate the two spacecraft.
One of the reasons the CBM was chosen for the resupply ships (including Dragon) is that the CBM has a larger inside diameter and so larger pieces of equipment (such as standard equipment racks) can be delivered through it, while the docking connectors cannot pass them.
One of the reasons the CBM was chosen for the resupply ships (including Dragon) is that the CBM has a larger inside diameter and so larger pieces of equipment (such as standard equipment racks) can be delivered through it, while the docking connectors cannot pass them.