Armstronglvs is correct and also incorrect. It is a doped sport but that doesn't mean that every great performance is due to doping. The comparison with Ryun keeps coming up with the question of how a younger kid could run as fast as a great prodigy like Ryun did. I don't have a problem believing it's possible and could be done cleanly.
In the first place, this isn't Jim Ryun's 3:58. Sam Ruthe has faster tracks and shoes than Ryun did. He had what was essentially professional pace making. Ryun did not. I'd say that with the same circumstances Ryun had Sam's time might have been in the 4:02-4:04 range, still tremendous but maybe not enough to set someone like Armstronglvs into a tizzy.
This is not a knock on Bob Timmons who got some very good results outside of Ryun. But he was a swimming coach feeling his way into coaching runners. Craig Kirkwood figured out how to train as a high school kid and did it well enough to get a scholarship to the University of Oklahoma, then went on to race in Europe for a while while living and training with some of the best track runners of the time. So I think Ruthe had better coaching than Ryun did.
Sam has a training partner who's run under 3:50 for the mile and was a 1500 meter Olympic finalist and another who is a gold medallist in the triathlon. Ryun trained with high school kids. It's pretty commonly believed that training with a good group can have a lot of benefits.
Finally, I read a longish article about Sam and the Ruthe family in an online New Zealand newspaper a couple days ago. They just seem as far from being the kind of parents who would sacrifice their kids' well being for any level of athletic achievement as can be.
Of course if you're really committed to believing that doping is the only way to achieve something spectacular in this sport you'll reject any explanations as to how the athlete managed to achieve what he has that doesn't involve doping.