This is really silly.
There would be very, very few true current world-class marathon runners who could run a 4 min. mile when prepared. Even Steve Jones, who wasn't exactly a speed merchant ran about 4 flat in the Emsley Carr Mile in England, after establishing himself as a distance runner, and he was never a 4 min runner like Hall when he was younger.
It's most unlikely that Hall thought he was going to run a 4:00 (or near it) last week. I suspect he was doing to go with his wife, have some fun, and get a feel of the pace, and just pushed it early to take the guys out at a decent pace, then shut it down.
There would be no question that a guy like this can get back to run what he did in college if he has time to focus on it. True world-class distance runners are not plodders.
I remember a top English marathon runner, Mike Gratton, turning up to run against us for his club in a track league meet. He filled in on the last leg in the 4 x 400m. We had a decent (say 51:0ish) runner on the last leg, and thought it was going to be hilarious, but Gratton dusted him and ran near 50:00 flat on a bad cinder track.