I watched the video, it wasn't a perfect race; he had to push too hard for the lead which caused him to go out in 25 for the first 200. He ran from 400 to 600 like he was shot out of a cannon, the 3rd 200 is usually where you gather yourself for the penultimate 200, which is usually the fastest. This is a tough kid, he was totally lactic coming off the final turn and I could see him battling the 800m-death-march all the way to the finish line with no one in sight. Put him in a paced race with better athletes, no 800m rounds and a 1500m the day before and he could have run 1:48x. I have not seen the Max Burgin WR race, but I know it was paced by Michael Rimmer, so I am assuming is was probably against senior competition and he didn't have to run rounds and other events.
Hopefully after the AAU's, he takes some time off, a couple weeks of chilling before starting XC training. Unfortunately, I have a felling he may take another shot at that 800m WR. Grandville didn't leave any food on the table either when it came to age group records. Up to age 18, he didn't finish a season without an age group or grade record, but it cost him. Grandville had a good NCAA career, but he never ran faster than his high school record.