He may also have had some instruction or training in dealing with heights, either on-the-job or recreationally. There are learnable techniques in walking confidently and easily on narrow surfaces or with uncertain footing that he could have picked up from Scouting or similar activities, or he may just be a person with spatial confidence in situations many others find harrowing. Think of gymnasts who learn to maneuver easily on balance beams, or of stunt artists and daredevils on highwires, or of non-performers, non-athletes, "just ordinary folks" who feel at ease rock-hopping or climbing mountains or walking narrow trails with precipitous drops such as those found at the Grand Canyon and many other parks. And then there are people in various places around the world who are used to walking narrow rope or log bridges just to get to where they have to go. It's not that unusual, it's just a matter of acclimating to being on a narrow or flimsy high surface and either overcoming the novice's fear, or never really feeling it in the first place.