No opinion on berian himself. I would make the observation that vast majority of collegiately successful 800 runners max out at the 1:45 high 1:46 low point. This seems to happen regardless of 400 speed, high school pr, etc.
There are dozens of 47.x/ 1:52 high schoolers every year. Very very few of them will ever touch 1:44 much less 1:43. I ran with a guy with 47. / 1:48.x hs prs at one of the premier mid distance programs in the country. He worked his ass off for four years, won a bunch of conference titles, became an all American but never went under 1:46.
Breaking 1:44 takes true wc talent and training. It's unfortunate that questions have to be asked but that's just the nature of the game right now'