1. Alex Honnold's brain is atypical. His amygdala simply does not respond to stimuli the way that it does in most people. To learn more, read this (excellent) article:
http://nautil.us/issue/39/sport/the-strange-brain-of-the-wor...
2. While I am (at best) a mediocre climber, the section you quoted rings true to me, particularly this section - "Climbing is an intimate relationship with our world’s most dramatic landscapes, not a self-boasting fight against them." There is something incredibly natural and sensual about climbing on rock that I can't describe without sounding like I'm talking about sex. And...that's traditionally where people tell me to give them my keys because I've had too much to drink. :)
3. Climbing is a deeply meditative activity, particularly when you get into a place where each movement flows into the next. When I am there, my mind shuts down and it is just a rock and me doing the most natural thing that I have ever found (see #2). That flow is deeply beautiful, but when you climb with ropes, you have to be in near constant contact with your belay partner. When I am with my regular belay partner, it interrupts that flow. When I am with a new belay partner, I never get close to it.
I suspect that if my amygdala worked like his, I would free solo simply to avoid having to communicate with a belay partner.