Yeah I found this assertion pretty troubling too. The "black" on most displays is already "soft" since even black pixels are leaking light. I've never read a page in a book and thought "you know, this ink is too black, it's straining my eyes".
I've never thought the ink in a book was too black, but once in a while, I do think the paper is too white. Usually actual paper is a lot more friendly than #FFFFFF, though.
