People often don't report minor accidents. Someone scrapes a pole without causing enough damage to hit their insurance deductible, are they going to file a police report? Mostly not. And then the older number had that in it and the newer one doesn't.

But the number for human drivers works like the old number. They're dividing miles driven by reported accidents. On top of that, they're using the average -- by miles -- which isn't the same as the median, and in particular that will over-represent drivers who drive the most miles, who are disproportionately professional drivers.