Impressive I think. As far as I understand he has been training well for approx 12 months more or less. He does very solid training, obviously based on the Ingebrigtsen model (but different from the 3 fast younger brothers).
What is also obvious is that he as genetically probably the same as his brothers. He did sports on his young days, but quit at some time quite early.
I think this falls within the same example as many who have picked up running in adult years and gotten to a high performance quite fast. Genetics play a big role at what level one can reach. He is 32 and is far from having some effect of decline.
This is a great story and I congratulate him. He is inspiring many and that it is never to late to pick up running and get a very good time pursuing reachable goals!
I think he needs to adjust his threshold paces now. He has been doing 3.45-3.40 paces for 1-2-3k reps, but a 3.35 HM, he needs to adjust at least 5 sec :-)
He does after a progression over a long time 100k a week. 3 workouts in total approx 100min of fast work (3.45-3.40), one long run of 85min (4.40) and else an easy run of 55min (4.40). Simple and effective to develop running.
No faster work, no hill work, no sprints, no faster than race-pace training, no weights as I understand. Just plain efficient aerobic training work based on (sub) threshold reps from 3.40-10min