The users can restart Windows to force Shadow Defender to clear the changes, even with activated Fast Startup. But, this cannot be done when the user will shut down the computer.
When the Fast Startup is turned on, then the computer shut down means only that all users are logged off (no logged users, no started applications), but still, the Windows kernel is loaded and the system session is running. Next, Windows saves the current system state to the hibernation file, and turns off the computer. If the user starts the computer next time, then the system state is restored, but the system is not restarted. So, Shadow Defender session is continued just like the user did not turn off the computer.