How many threads have been here over the years from people wanting, and getting, predictions about how fast they can run for a specific distance based on a workout or series of workouts they've done? Loads of them, right? Running now is crawling with formulas and people who believe in them. So if Hall is doing the kinds of workouts he was doing when he was running well under 2:10 it's reasonable that he honestly believes he's ready to run well under 2:10 again. Hence the comments about how well he's running and how well he plans to do.
The trouble with that kind of thinking is that racing is different from training and turning in monster workouts does not mean you'll run monster races. The best way of knowing what sort of racing performances you're capable of is by racing and Hall, like many, maybe most, top level guys these days, doesn't do very much of that.
I don't think there's anything mysterious here. He's probably capable of running marathons in the 2:12-2:15 range right now, maybe even a tad faster under ideal conditions, which he evidently did not have yesterday. But his history and perhaps recent training have him convinced that he's capable of much more than that and when he sets off at a pace that he believes he's ready for but really isn't the result is the same as when a 3:30 guy sets off at 3:00 pace.