When a multibranch pipeline job, the deleted branches and closed PRs get striked-out but they do no get removed automatically. This results in disk space being consumed for those obsolete branches and PRs. Orphaned Stategy is set as 'Discard old items' checked, with no values in 'Days to keep old items' or 'Max # of old items to keep'.

However, when I manually trigger "Scan Repository Now", all striked-out branches and PRs get removed.

Why are those branches/PRs not getting deleted instead of just being striked out ? How can the cleanup be handled automatically ?