If I use Search > Find... from the drop down menus WITHOUT "Search Backwards" select it searches forward (from top to bottom) as expected.
Likewise, if repeat the operation WITH "Search Backwards" selected, it will search upwards, just as I would expect.
If you select Search > Repeat Last Find it works in exactly the same manner, searching forward if "Search Backwards" is not checked and searching backwards if it is selected.
However, if you perform a Repeat Last Find by using the shortcut keys Shift + F3, it will work exactly backwards. In other words, if Search Backwards is selected it will search forwards, and if not selected it will search backwards.