First of all, Ryun took 2 minutes between 440 reps. They were run with 3:00 departure times, going by a big swimming clock by the side of the track. Bob Timmons coached state champions in swimming, cross country, and track. He coached Archie San Romani Jr, who had the national mile record at 4:08 quite a few years before Ryun came alone. Timmons also coached a number of national class swimmers, some of whom went on to break world records and compete in the Olympics.
I ran on the track at Wichita East a number of times prior to and when Ryun was there and it was always in excellent condition. You wore spikes and did not slip on the surface. I have run on gravel tracks where you slip a lot especially wearing flats but the WE track was not like that. Also Ryun ran a lot of his races on rubberized tracks. They were not all on cinders, but the cinder tracks were very fast too. And they were definitely easier on the legs.
I miss the dirt tracks and refuse to train on a hard rubberized track. They are fine for racing but usless for training and there are many better places to train.