There’s more than just that location
HKLM\System\CurrentControlSet\Control\Session Manager value: PendingFileRenameOperations
HKLM\Software\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\RebootRequired
HKLM\Software\Microsoft\Windows\CurrentVersion\Component Based Servicing\RebootPending
HKLM\Software\Microsoft\Updates value: UpdateExeVolatile