Craig,
I believe the documentation says that the USB controller is not a full OTG controller. It is dual role and can be used either as peripheral controller or as Host controller.
The ID bit is present in the OTGSC register because the controller IP does support full OTG functionality. It is just not implemented in Vybrid. Considder this a documentation issue. I'll mark it for correction in the next revision of the manual.
If your application does need to know whether an A- or B-type plug is inserted, you can use a GPIO imput with a pull-up resistor to determine the state of the connector's ID pin and configure the controller accordingly.
Best regards,
Richard