Question : What does the "shutdown" command do if updates are waiting?

A GUI shutdown will query the user to "install updates and shutdown". What will happen if the "shutdown -s" command is used? Is there an command option to force the updates install?

Answer : What does the "shutdown" command do if updates are waiting?

If you check out the System log - you will see entries for NtServicePack - if the update(s) installed.