These were early hybrid desktop drives when people did not have sata power cables inside their desktops, so they gave you a choice of power connections, Do Not connect both of them at the same time! It will smoke the drive, don't ask how I know this... WD gave no clear warning on the consequences of doing it either.
The Molex connector was discontinued on Sata drives for obvious reasons. They started shipping sata to molex adapters with sata drives instead.
FlexPower: Connector technology that accepts power from either industry standard or new SATA power supplies.
