Always found it a bit strange that USB-C is referred to as a "new connector" when it clearly seems to be an entirely new protocol. (Unlike the previous new connectors mini and micro which were just differently-shaped plugs for the same wires)
So is the protocol technically USB 4.0 and USB-C "just" a new connector role defined by that protocol, or did they ditch the versioning and "USB-C" is its own thing?
The guide mentions that USB 4.0 is the first version to require a USB-C connector, but then later refers to the "USB-C protocol". Is that the same as USB 4.0?
USB-C is a connector. Part of the confusion is that USB specification versions have come to be associated with the protocols and speeds defined there. The basic division is between USB2 and USB3 which are separate protocols on different wires. USB-C has multiple high speed lanes.
USB 3.0 defined the SuperSpeed protocol and 5GBps speed. Later versions increased speeds, 10GBps (USB3.1), 20GBps (USB3.2). These were also called Gen1, Gen2, or now just the speeds.
Then, there are alternate modes which run other protocols over high speed lanes. DisplayPort is the most common one.
Next, USB4 defined USB4 protocol which multiplexes SuperSpeed and DisplayPort over two high speed lanes. USB4 requires USB-C. This is basically Thunderbolt standardized. Specification also defines 20Gbps, 40Gbps, and 80Gbps speeds.
Perhaps you will find page 27, "USB signals over USB Type-C®", clears up the strangeness.
At least when you get to the first section, "USB 2.0 Signaling Over Type-C".