Aaah, my interests intersect.
I sport climb and boulder (the same disciplines as Kessler)at a level equivalent to a 21-22 minute 5K hobbyjogger. I was a 17:XX runner. After I got injured running, I took up climbing as a side interest. It stuck.
Climbing does not offer super-special mental gifts above what elite running does. Think of runners like Billy Mills who used visualization as a key tool, guys like Adam Goucher who are tough as nails, and masters of the sport like Eliud Kipchoge who bring it all together in a Zen-like master package. All of these archetypes have their own equivalent in the climbing community.
Sport climbing is NOT where I would expect to find an elite runner. Gymnastics would be a much more likely candidate. If I were looking in track and field, I'd expect climbers to succeed at something like the pole vault.
This shows Kessler is a special, special athlete. Imagine being a national class gymnast and running a 3:51 mile. It's just such different physical skill sets, yet he can do both.
What it probably means is that if he were inclined, he could put up routes in the alpine that no one else could. The mix of cardiovascular strength and technical excellence required to put up hard, long routes in the mountains is rare.
By his performances so far, he is a better runner than climber. Climbing 5.14c is probably roughly the equivalent of running somewhere around 4:00-4:05 for the mile. With much more lifetime experience on the rock than on the track, I'd guess his highest ceiling is there.