It it’s a laptop, possibly not. It might be suspending to disk. Although you’d notice: you’d get the session back as you left it. So I guess my question was silly.
Look in the BIOS settings: sometimes you find “legacy USB” options or some such there. Also, if you’re not interested in charging stuff when the computer is off, sometimes there are also options to power down the USB sockets when the machine is off - which would power down the KBR1 and force a re-enumeration at the next bootup.