Why the Sorter transformation is an active transformation?

Actually the Sorter transformation helps to sort the data in ascending or descending order. And hence the number of input rows to the Sorter transformation remains the same as the output rows.

But the Sorter transformation has an option "Distinct", using this option we can remove duplicate records. The number of records can changed, if the source contains duplicate rows. So the Sorter transformation is an active transformation.