Looks like "Offline authentication" is a reference to Encrypted Offline Cache... and the same can be achieved with JSONStore as well.
Source: Enhancing Your Mobile Enterprise Security with IBM Worklight
Offline authentication
When applications are running on mobile devices that are not connected to the network, the need for user authentication still exists. The encrypted cache feature in Worklight can be used to achieve more offline authentication because only the correct passwords can unlock the offline cache.
Theoretically you could devise an authentication flow that uses local secure storage for authentication needs.... I don't know how popular that would be...