This looks like JD's so called '3 year' dependability study, where the average age of a car in the study is about two years old. In my mind this is an initial quality study. Dependability is a matter of quality in cars at least five years old, and hopefully closer to 10. Just my opinion of course, but then I don't switch out cars every three years. Heck, our 1996 Subaru has just entered middle age.
The problem is that the 2006 Prius is a midsized car. Putting it where it belongs, the Toyota Matrix takes the Compact class. The 2006 Buick LaCrosse ties with the Prius. Maybe I'll believe a Buick can stand up to a Toyota for 3 years--if GM had a massive quality overhaul since 2000. No way it'll hold up to a Prius in the longer run. IMO it feels like they moved the competition so GM can claim a win.