If you actually sat and read it, you'd see that it's a piece of software that sits on each device connected to the USB switch and detects the USB disconnect/reconnect events which trigger when the USB switch is triggered and uses them to detect that the device should try to take control of the display devices.
I sat and read it and I had the same confusion. I've used a KVM before, but never knew that was some version of a KVM without the "V" called a USB switch. It seems like that peripheral must be less common than both USB hubs and real KVMs.
