There is a very important difference. Redundancy doesn't protect you against bad changes to your data, backups do. Backups should ideally be immutable, and append only. What happens when a disgruntled employee runs 'sudo rm -rf /'? With redundancy the effects of that decision are dutifully cloned on all media. With backups one has the ability to rollback to an older state.
Backups are redundancy out of firing range of problems like, say, hard drive meltdown, operator error, etc.
I've had gruntled employees, occasionally myself, run some variant of 'rm -rf' unintentionally far more often than I've had to deal with the other sort.
If you feel my grandparent post was advocating against backups, I'd strongly suggest you re-parse it. It's distinguishing between varieties of redundancy.