Good question, so I've written Roland for an answer. I did notice the following:
"Some players like levers or wheels, while others prefer external pedals. With FANTOM-0, you can use any of them—or all of them. And there’s even a dedicated USB device port to extend your workflow with your favorite USB MIDI controller."
MIDI 2.0 already has a definition for sending 2.0 data packets over USB, so perhaps this is intended to allow future compatibility with various MIDI 2.0 functionality. My guess (in the immortal words of Herman Cain, "I don't have facts to back this up") is that it has the hooks needed for MIDI 2.0, but they're not promoting it because there's still nothing to hook into that's available to the public.
“Hopefully there’ll be an operating system upgrade sometime in the future to implement MIDI 2, even if it’s just to respond to the CI with “this device is MIDI 1.0 compliant”!