Why do you think you should get an exception? Just because you know a lot about trains? Sorry, the world the doesn't work that way.
I feel like I am able to travel alone on Amtrak. I handle all Amtrak travel for over 100 family members, I'm even writing a book about traveling on Amtrak. I think there should be an interview to see if a child is capable of traveling on their own. Maybe I'm wrong, and I'm not capable, but since I'm in charge of everything when traveling with family on a train, and never once have I booked the wrong ticket, station, been on the wrong train, or been left behind.
To be effective, a policy must be short, simple, and easy to understand and implement with little room for misinterpretation (an interview would be both impractical and much too subjective). It cannot allow for every contingency, but that means some persons such as yourself - who may very well be able to travel alone - cannot get an exception.
Theme parks often set height requirements for attractions, even though some six year old kids are taller than some eight year old children.
You must be 18 to vote, even if you know more about the issues than most adults.
The unaccompanied minor restriction is in place for a reason; Not because of your ability to travel alone, but because many persons your age should not.