Keep in mind in the previous deepest 800 race, the 2012 final, there were fewer athletes in the field (this one had so many for some reason?) and they had the rounds in their legs. There's clearly been time to cut off for a long time.
With that said, 3 1:41s is nuts. And then 3 more 1:42s. Immediate thoughts are the 800 is back. Bryce Hoppel has a much longer shot at a medal now. He's got at least a 1:42 low in him on fresh legs, but apparently so do like 6 other guys. Also I don't think Kessler has as good a shot in the 800 as we thought a week ago. Maybe he could pop a 1:42 high in a perfect race a la Clayton Murphy in 2016, but I don't think his chances in the 800 are any better than his chances in the 1500 now.