These are additional notes in line with tr3bjockey's observations, and expanding on what I think the failing mechanism is.
16gb USB2 data traveler by Kingston, stuck on synching. While I was waiting I plugged in another already configured UNRAID usb flash drive to look at the file structure -- and the flash drive creator tool immediate saw the old already named and configured UNRAID flash drive appear and overwrote it with a new installation (this was disappointing as it had been the configured installation of a trial).
I removed my old UNRAID flash drive that had just been overwritten by the creator utility, and tried running the creator utility again. It again hung on synching, so I tried renaming the flash drive UNRAID (it was called something generic like "USB Drive") and the utility immediately saw it and completed.
So .. it appears that the flash drive creator is programmed to rename the flash drive to UNRAID and then to continue working on whatever drive is called UNRAID. For some drives, perhaps some that don't have a name it understands, it fails to rename it and therefore waits forever for an UNRAID drive to appear --- unless you rename it yourself.
Also -- It gave my 16gb drive a single partition of 8gb. My understanding is that this doesn't really matter as the space needs are unlikely to exceed a few megabytes, but it is still disappointing. I would imagine doing a manual install would fix this as well.
The irony is that I chose this drive as I believed it was one of annointed (recommended) ones. I could have had a larger and faster (USB3) drive for about the same price, but I was trying to play it safe. Hopefully it will be rock solid going forward. I'm hoping the metal construction and its size (small but not too small) will mean it won't get too hot or burn out early.