Caveat: Not all USB 2.0 is what you expect. The correct term is "High Speed USB" which means 480 Mb/sec. "Full Speed USB" is the slow 12 Mb/sec flavor, and it is legal to call it either USB 2.0 or USB 1.1. The original version 1.0 is even slower, and those devices are rarely seen these days.

The ostensible reason that you can use the term "2.0" to describe a slow "Full Speed" device is that a Full Speed USB device will work when plugged into a High Speed port...of course, it will only work at the slow rate.

USB.org used to have a press release posted that explained this anomaly, but they must have been embarrassed because it is no longer available. It's a real screw-up, but is fading from importance as more devices are genuine High Speed.