Stop sharing Macintosh HD and home folder with File Sharing?
Turn off Volume shares (on by default)
sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.smb.server VirtualAdminShares -bool NO
Turn off User shares (on by default)
sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.smb.server VirtualHomeShares -bool NO
Then reboot your Mac. I've tried a few combinations of using launchctl unload -w on the smbd service, but the shares stayed open until I rebooted :(