Yeah, I thought that line was weird. It's more like – you can change the record's internal foreign key without breaking your users! Once users have bookmarks, IDs more or less permanent.
Naturally it depends on the data. I've used it when we want to show the most recent version of a record on the public website but we want to keep older copies of of the data to reference with past events. Eg customer's current address can always be identified with id x but the address records for specific past orders reference other records.
