@Chris > You're confusing the situation.
If you network all of your players and mixer together, you connect the USB ONLY from the DJM to the computer and you can have all that communication established over the one cable.
This allows for either USB HID control (for rekordbox DJ in performance mode), or LINK connection (with rekordbox in export mode).
When you connect the SP1 to one of the CDJs' top ports (where you would connect a USB drive) you can control the hot cues, etc. of the players -- this is ONLY for LINK mode. If you want to use the SP1 to control rekordbox, it has to be connected via the computer.