The author states that there is a difference in the opening, and I agree.
I have never done a 'thru-hike' but have done two 6-month backpacking trips, and many shorter ones over the years. I have been tinkering with the idea of doing the PCT when I retire, but I am not sure I will be happy living away from the wife for that long.
Thinking back to my first lengthy trip in 1971, here are some of the differences in my mind:
The goal - for me was to hike for a period of time, which was not defined. I figured that when it was time to go home, I would know it. There was one limitation, I was not prepared or interested in staying the the Sierras in winter. So the trip would probably end in September or October. I started in April. For a thru-hiker, the goal is point A to point B. So you set yourself up for failure or success from day one. On my trip there was no destination.
Time - a thru hike requires a detailed plan on how to get from A to B. It must include logistics for food and weather (snow in the Sierras, as this year) that can be obstacles. For me, I needed food every couple hundred miles, sometimes longer because I had the luxury to fish for trout almost everyday. Also, time includes stress to get back to a job, school, or other commitments. For me, I had just gotten out of the military, had zero obligations and had a couple thousand dollars in the bank, which is probably over $10K in today's money.
Planning - a thru hike requires a lot of logistics to meet the time and food issue. For me, I just needed a map to show how close the next town was when food got low, and I had no idea where I might be in two weeks, a month, or even longer.
Social aspect - for many thru-hikers this is a big part of the adventure. Thus, we have "trail names, trail angels, and hiker havens." My goal was to avoid as many people as possible, to leave the human aspect behind as much as possible. To be honest, when I started, I really knew nothing about the John Muir Trail, other than it was marked on my forest service map. Once I got around the Whitney area, I decided to go to Yosemite via the JMT. Once I got near Yosemite, the crowds turned me off and I turned around and went back, although with many, many scenic detours. I never had any desire to return to Yosemite until around 2004, when my son wanted to visit. And it was worse than I expected, other than the overwhelming scenery.
Spontaneity - not a lot of leeway on the thru-hike. There are time tables to meet. For me, if I found a wonderful place, I might stay there for a few days or even a week.
So I finished the trip in mid-September, because it felt like time to go back. And the trip was successful, because the only goal was to enjoy whatever felt right each day. Highly recommended approach.