Yes, it's true that chef/puppet do not overwrite your entire etc, just a subset of it, but presumably, you'll have your critical components backed by it (otherwise, there is not much point in using a configuration management system). So it is still useful on such a system, but not to the same extent of a system without configuration management.
> but presumably, you'll have your critical components backed by it
Often, the way you discover something is critical is after the first time it breaks. Backups may help, but proper version history is probably going to give better insight into what happened.
