knowing those corporate entities, they probably were forced to ship the device by a certain date, with incomplete drivers or firmware, therefore the "coming soon" blurb for OS9 support... they probably intended to get it working fully later, and afterwards, probably due to low sales, the bean-counters re-assigned those developers to other projects. Ive seen plenty of cases in the past where some piece of software was advertised to work with something, and it didnt come till a later update.
i can tell you, as I was active in the computer audio scene even back in those days, that the Opcode USB interfaces came out right at the time that they were acquired by Gibson, and we all know how that turned out for the company. Many of the USB devices they announced never even made it out the door, or if they did, were in miniscule quantities. I think its extremely likely that something akin to the scenario I described above played out with this device's development.