At the switching frequency of a typical POL converter, that ESR keeps the AC voltage ripple below a few millivolts, which means the downstream load sees clean DC without an extra LC filter stage.
680 µF at 6.3 V provides bulk charge storage for low-voltage rails, holding the rail up through a load transient.
The molded case (Type Molded) handles the thermal expansion cycling without cracking the dielectric.
This part can be specified for new designs without planning a migration path.
