The latest BIOS release will support 3TB HDD booting. You will need to use the latest @BIOS from Gigabyte website for updating the original BIOS to EFI-enabled BIOS.
The Gigabyte site said the board had a 'dual' 32Mbit (4MB) Flash ROMs, so it felt like the hardware had some flexibility designed into it. I suspected the beta BIOS was EFI
I wrote to Gigabyte tech support a week ago, but no response.
My next curiousity is whether the implementation is EFI on top of BIOS, or purely EFI
As of tonight, the EFI BIOS is still beta, but thank you very much for the tip about @BIOS when switching to EFI.