One of Tufte's main themes was, I thought, that only information that directly conveys meaning should be included, and everything else should be thrown out. Where everything else, in the context of UI design, would probably be excess styling. On the other hand, I forget where I read it but we know that people are biased into finding more attractive interfaces more usable, even if a "usability expert" might disagree. So personally, I find Tufte's title fitting - he really is talking about effectively displaying quantitative information.