So the scenario (as described by waymo, surely with some spin): "Driving through a 4 way intersection, while a large truck is also going through the intersection. As you go through, a biker quickly passes behind the truck with minimal time to react once in sightlines." A human driver would take significantly longer to react, and could be deadly. Waymo managed to hit the breaks before the collision, potentially leadin…
It could have been absolutely unavoidable but I don't think we know that now.