Thanks,
I think a large part of their reluctance to acknowledge the existence of all those small craters in the southwest, is because mainstream planetary science is a little too fond of the hypothesis that you can estimate the age of a planetary surface by counting the number of craters. There is an awful lot of planetary chronology that’s founded on the assumption that impacts happen at a steady rate. So the very idea of a cluster impact event plays hell with their thinking.
Thanks to more than a century, and a half, of uniformitarian / gradualist assumptive reasoning in the Earth Sciences, they assume without question that all planetary surfaces in the solar system are subjected to a steady flux of impacts. They also assume that a normal catastrophic impact event is a single, large bolide. And that such catastrophes are the rarest of the rare.
But the crater fields of the American Southwest that we can see clearly with Google Earth, and which are all in the same very good condition tell us their assumptions of a slow, and steady, impact rate are a naïve as a children's fairy tail.