Companies measure multiple disengagement rates for different purposes. The DMV numbers are usually safety rate numbers, as in "if a human hadn't intervened there may have been an accident or near miss". The specifics vary company-to-company, and they'll have a large document somewhere laying out exactly what the criteria are. The numbers in the article are some other metric, though I have no idea what. I'm a bit skeptical that it's the average over their entire ODD, given that it's much higher than my own experiences and most of their vehicles were running around the outer city at night, where they seemingly did okay.

It could reflect some particular ODD (e.g. downtown at rush hour) where the vehicles didn't do nearly as well, or something else entirely.