I like these analogies a lot. I regularly have to explain to my clients the difference between the backup system, the disaster recovery system, and the file server replication system. None of them is the same as any other, and each component has different levels of redundancy going down the stack (RAID, HA for the virtual machine, shared storage between hosts, etc) and it's no easy task to explain that yes, while component X is redundant, it does not meet the definition of "highly available" or "backed up." So I appreciate any explanation like this article that attempts to simplify and illustrate any of these definitions.