Seriously I get the excitement. When Miller ran this same basic time (he is like 6 months older than Sumner) last year, it was a sign he was going to run a fast 800. But 1:45 is a long way from 1:42.3. I hope they both get there. But it is far from assured.
Has anyone heard how Flatts training has gone other than that he's running at Millrose? Great result for Sumner. Examples of fast 600s correlating with 800s in the same season: Saruni(doper now) 600: 1:14.79 and 1:45.15 indoor 800. Isaiah Harris: 600m 1:14.96 to 1:44.53 outdoors. Korir: 1:14.97 to 1:43.73 outdoors. Jones last year 1:15.12 and 1:45.83 outdoors. If Sumner doesn't run at least 1:46 indoors and 1:45 outdoors this year I'd be surprised.