I'm fairly sure that this is the way that members of the Royal Family see their honorary military appointments. In Edward's case, I'd guess that he's very much aware of all the criticism that he got for leaving the Royal Marines. Sometimes I wonder how he would have gotten along had he trained for one of the other services, because the Marine training is supposed to be the toughest.
The only difference would be that Edward's route into the Marines changed him. If he was in the army or the air force he could have gone straight in from gap year and he would probably still be there now.
Personally and I know that I will be corrected on this. Edward took the wrong route into the Marines. He took a programme that allow prospective officers to attend university and train during weekends and vacations to be Marines. Now that is a difficult programme to follow for anyone but it was a near impossibility for a royal.
Edward's first year saw him participating in more extramural activities (you'll remember that he was still completing his gold Edinburgh Award) so he was doing rugby, royal tennis and drama. He was also collected money for the Duke of Edinburgh Awards and undertaking royal engagements. Then on weekends and holidays the marines took over and he would skip for royal duties.
In his third year he was in charge of the Rag Week which collect money for charity. He had dropped rugby by now, but the rest of his schedule was the same. So that by the time he had passed his degree no one - notably his professors at Cambridge were surprised that he didn't do better. I am told that he simply wanted to cram as much into his time at uni as possible.
So by the time he reported to the Royal Marines he had spend three years of weekends and holidays with him. He already had passed the physical requirements, it was simply the course work for officers and then he would have gotten his commission. But by now he knew that the marines was not for him. His answer from the day he left the marines till today remains that at 17 when he joined up he was absolutely committed to the marines, at 21 he was no longer that person.
Millions of people around the world have left the armed services, they are not cowards or anything else for this. Just as simply as the billions of us that have never thought of been in the military are not. But it is generally thought that there is a conscription imposed on royal males close to the throne, I can believe that, and I am glad Edward rebelled against it.