What is meant by the RMAN Duplicate "noncurrent point in time"? When doing a RMAN DUPLICATE from backup connected to the target, how current does the duplication make the database when no until time is set?

The closest thing I can find in the documentation is the following statement:


  Restores and copies the duplicate data files and recovers them with
  incremental backups and archived redo log files to a non-current point
  in time.


How current is this non-current point in time? Does it apply to all the Archive Logs it has available to it at the start of the duplicate, or are they perhaps only available when it reaches the recovery part of the duplicate?
It's the moment of the last redolog archival, before some point in time during the RMAN duplicate command. You can test this easily, if you either manually provoke redolog switches (and thus subsequent archivals), or even better: write some script to provoke very frequent and unnecessary redolog switches. In which you perform some insert/update/delete, to further track things down.