Ratings Debate

The PBS Ombudsman, Michael Getler, takes on the language PBS used in promoting its ratings for the new Ken Burns documentary, "The War." (The film, by the way, is well worth a watch.)
The piece provides insight into the ratings game and how it's played. I'm fascinated because PBS isn't in the same fall ratings race as the other networks, which rely on ratings to set advertising rates. One normally wouldn't expect public television to hype viewership. Why would they in this case? What's fair in promoting ratings? Does it ultimately matter to the audience?