In my recently deleted questions, those that have been marked as duplicates show up as "[on hold]" or "[closed]", which should show up as "[duplicate]". Examples:
A question that was marked as a duplicate less than 5 days ago and later deleted will show up as "[on hold]" in the recently deleted list:
A question that was marked as a duplicate more than 5 days ago and later deleted will show up as "[closed]" in the recently deleted question list:
However, when you click on such a question and view it, the "[duplicate]" indicator shows up properly:
Is this by design, or is it a bug?