How does DataStage Project Level Auto-Purge Job Logs Work

1. The job has to be run. I.e. if the job isn't run, its old logs will not be purged.
2. The job has to run successfully. E.g. if the job is aborted, its old logs will not be purged.

Someone mentioned to me that the project level auto-purge job logs only affects those jobs imported after auto-purge change. This doens't appear to be the behaviour with the version 8.5 I am working with.