Surely the backup is more likely to go wrong than the one liner! Instead a newbie should only be working unsupervised on a non-production machine and backups should be done daily (and in this case also on demand) by properly-qualified staff for all machines including non-production.

Moreover, Anybody, not just newbies, can make a mistake and it is rather comforting to have the capability to call your friendly sysadmin to restore the damaged goods back to a previous state if there's no quicker repair available.

I remember having a misunderstanding in a Q/A system over the first digit in an identifier once and deleting everything BUT the data I was supposed to be deleting. Fortunately, a phone call and ten minutes later it was back to where it was.