We recommend adding fall-back paths to variant criteria to ensure content isn't accidentally omitted from a published output, or to create time-based variant criteria, such as release version, product model, or year.
For example, if you have a variant criteria called Country, "Europe" could be used as a fall back value for various European countries. If an object didn't have a variant for "France" , the "Europe" variant would be published when "France" was selected as the value of a publishing job.
Alternatively, if you have a "Release version" variant criteria, representing the versions of an app, each version number could be a fall back value for the next version number. If an object had a variant for "Version 1" but not "Version 2", the "Version 1" variant would be published when "Version 2" was selected as the value of a publishing job.