Correct, in order to sync two VorTech pumps (master/slave), they both must be wireless. (They must each have an RF chip and the "W" must be lit up.)
You can sync them via a series of button presses, directions found in the PDF manuals or on various YouTube videos and via the EcoTech website. Otherwise, they can easily be synced via EcoSmart Live, if you are using a ReefLink.