I referred to the instructions mentioned in the documentation to archive a team and I was able to fully archive the team after running the command. What it means is that once the command is executed, I just need to refresh Mattermost and the team will be removed from the sidebar completely. Specific to this statement:
May I know which documentation / article you were referring to so we can revise the information?
Meanwhile, are you looking at having a built in feature in the Mattermost client UI that will allow administrators to archive / unarchive the team (without running the command manually in the terminal / command line)?