Question:  The Freespeak II base station user manual indicates that if the user upgrades via USB a .FWS file is used and if upgrades are done over the air (OTA) a .FWW file is used.  Is this correct?

Answer:  Yes this is correct.  The user manual 399G087C user guide describes the two procedures to upgrade beltpack firmware:
Upgrading using a USB connection
1) Connect the beltpack to a USB port on the computer running the Configuration Editor.
2) Select Diagnostics > Tools > Apply Wireless Firmware Via USB.
3) Browse to the location of the upgrade file (.FWS), and then select Update Firmware.
   The upgrade file is downloaded to the beltpack.
Note: You can connect more than one beltpack to the computer if you have multiple USB ports. The units will be upgraded sequentially.
Upgrading by Over The Air Upgrade
1) From the Configuration Editor, Select Send File, and then browse to the location of the upgrade file (.FWW).
2) Select Open. The download will begin. The beltpacks will be disconnected while the download file is loaded onto the antennas.
   The beltpacks will only be upgraded, when the download file has successfully loaded on all the connected antennas.
Note: The Base station front panel will display a download progress screen.
3) To cancel the download, press Enter on the Base station.