Yea I have tried the function without calling __FFSetTopDocument and it works with no difference !
Also I have tried alone the __FFSetTopDocument function on a visible down-scrolled webpage, and absolutely no effect it has ! It doesn't scroll the page up to the top. Thats why I was asking here about it, since I see its so useless..lol
I think the author is the only one that will be able to give us a clue on that function