Change in microsoft documentation
From the same documentation:


  Beginning in SQL Server 2014, readable secondary replicas can remain
  online even when the primary replica is offline due to user action or
  a failure. However, read-only routing does not work in this situation
  because the availability group listener is offline as well. Clients
  must connect directly to the read-only secondary replicas for
  read-only workloads.


So, you can go to 2014 because the article exists only for 2016.