A lot of the "rules" about running go out the window when talking about high school athletes. Hobbs Kessler ran 3:34 with a 1:49 800 and 8:39 2-mile, and only a 3:40 1500 PB coming in. Conventional wisdom says that should've been impossible - Webb himself ran 1:47 and 8:42 and his mile was noticeably slower. There are very few pros with a sub-3:35 PB who haven't also run 1:45-1:47, and the only ones who have done it also have sub-13:00 5k PBs.
So I would hesitate to put any high school athlete in a box. Crazy improvements and unusual times are pretty much the norm. If you said a year ago today that Tayvon Kitchen (a 4:11 guy) was going to run 3:41 and 3:59, you would be instantly dismissed. He had a 1:59 800 PB at this point last year, now he can do it twice. Clearly, he is still on the steep part of his improvement curve, and another 7 seconds could be possible. Josiah, meanwhile, has run 1:51 in a lowkey meet this season, and 3:57 indoors. Going under 1:50 is likely only a matter of time for him - would you not think a sub-1:50, sub-8:00 guy would have a shot at 3:53? I only knew a few guys in college who accomplished both, and all of them ran at least 3:38...putting them within spitting distance for sure.
TL;DR: not likely, but not impossible, and I'm glad they are going for it. It's an awesome record that deserves worthy challengers every year until it goes.