This advice is only somewhat true.

Whether or not a particular machine allows cron to be run from user accounts depends on how that machine is configured. Look up the crontab command on your machine. Generally there can be files (on mine /etc/cron.allow and /etc/cron.deny) which control who can use cron. In general it is not a good idea to have critical production jobs running from user accounts. Have production users for that...

Also note that crons are something which I do not recommend editing directly. They are usually important, and are too easy to mess up. Instead have a file under version control (which I tend to name "crontab", YMMV) which you edit, and then do crontab crontab to install. That way if you do something wrong, you know you can get back to your old crontab very easily.

Many people use named backups of key files instead of real version control. It kind of works, but real version control is much, much better.