Long, long ago, before there was dirt, there was UnPropagate. In order for Select Duplicates to work, the records had to be sorted on the field you were checking for duplicates.
As I’m remembering it - you didn’t even need SelectDuplicates. You’d sort up on the field to cluster duplicate records together. Then you’d unpropagate which would empty that field for any records that had duplicate content. Then you’d select on that field not equal to empty, and finally RemoveUnselected. NOTE - this ASSUMES legitimate records would always have content in that field.
So six statements:
Select (YourField <> “”)
Select Duplicates, on the other hand, selects those duplicate records so you can manually review them and choose which ones to delete. For example, if you have another field that contains a “date added”, you’d want to keep the most recent and you could see which one it was. Of course, in that case, you could also sortwithin on that entry date field after you’ve sorted on YourField - putting the most recent record on top of its cluster.