Removing duplicates after sorting does not work as expected

So I have key column and a date column and i am trying to keep only last date for every key. I first sort by key column and then by date column descending, and everything is looking fine. But when I click on remove duplicates, it does not remove rows that I wanted to remove, for some keys it remove wrong rows.

Here is screenshot of table, after sorting, everything seems fine. I marked rows that are expected to be removed after I click on remove duplicates(based on key column).

But, instead row number 3 from first screenshot, row number 2 is removed.

Please, can someone explain me what is going on here?