I think it's a useful distinction to be clear about. The tabulators, processors, scanners, what have you were all definitely connected via netowrk. It would only take one of those devices to be open to the internet and they effectively all were. That's the purpose of the USB devices, to have an "air gap" between two computers that are not networked.

The USB devices themselves create a vulnerablility though (example: Stuxnet). I worked at a defense contractor a few years ago and all of our computers were replaced to disable USB ports and CD/DVD drives to remove vulnerabilities.