SQL Server secondary replica snapshot with Basic Availability Group
That link refers to taking a Database Snapshot of the secondary database, which was possible in Database Mirroring.

Remember there are lots of unrelated things that use the word "snapshot" in SQL Server:


  Database snapshots are unrelated to snapshot backups, snapshot
  isolation of transactions, or snapshot replication.


It's not possible to use a Snapshot Replication with a secondary database:


  In an availability group a secondary database cannot be a publisher.
  Republishing is only supported when transactional replication is
  combined with Always On availability groups.


Replication, change tracking, &amp; change data capture - Always On availability groups