This article was written in 2015. Nowadays most elite ultra-runners do have coaches, and follow data-driven training regimes. This is a trend in all professional (and, to a lesser degree, amateur) sports, but it is definitely quite noticeable in a sport where athletes used to basically be dudes and girls who liked running fast in the mountains and did that a lot. A lot of that data-driven training is aimed at maximizing training load without going into overtraining.

As a result of this and other optimizations (most notably higher carbs consumption during races, but also better heat training, better recovery protocols, better shoes, etc.), races keep getting faster. The article mentions the course record for the WS100 dropping by 50' between 2004 and 2012. Since then, it has dropped by another full hour (13h46 this year).