Easy to say he could have avoided it. I imagine the sheer shock/surprise of seeing a flying Honda may have taken up a little of his capacity!
Looking at the drop off to the right I think he should think himself lucky he didn't go over the side which is what I was kinda expecting, but I agree with Mike S he probably could have avoided it !
I was thinking the same, but then realised that the rider's vision would probably have not picked up all the camera did lens angles and all that- he likely focused on the road ahead, and in all fairness, who anticipates a large object falling towards them from above? Bad luck indeed. Hope the rider of the falling bike was ok, going by the speed that bike came tumbling.....