USB 1.0, 1.1, and 2.0 are revisions of a specification-- nothing more than a document that describes signalling, shielding, mechanical connections, and all the other specifications that make it work.
USB 1.0 was the original specification, released in 1995, supporting “low speed” (1.5 Mbps) and “full speed” (12 Mbps) connections.
USB 1.1 was a revision, essentially a “bug-fix” that worked all the kinks out of 1.0. This was released in 1998.
USB 2.0 added a specification for “hi-speed” (480 Mbps) connections in 2000. It also retained the revisions to low- and full- speed introduced in version 1.1.
Nothing was retroactively redefined. USB 2.0 has always contained specifications for all three signalling modes. In fact, the USB Forum has actively differentiated between high-speed and lower speed devices, and disallows using “USB 1.1” or “USB 2.0” to market devices :