Michael, I absolutely agree with you. "Date Posted" is a misleading heading for the column, and the creation date is unhelpful in this context anyway. Management of the moderation queue relies on knowing the date each item arrived there, and that's what "Date Posted" should be telling us.
I was told the current behaviour is as expected. In my view it's a flaw which ought to be fixed.
Our moderators also find it frustrating that the moderation queue can't be sorted on this or any other column.