I believe that there are two answers to the question "What is considered secret?".
First, there is what your GL tells you is secret. I think of this as the legal definition. I don't need to list them as a Mason will already know them.
Then there are those things that are secret because each man must discover them for himself. An example of this from the profane world would be happiness. I can define happiness for you, I can tell you what makes me happy, but I cannot tell you what makes you happy. Each man must discover this answer for himself. Freemasonry offers a path to these "inner" secrets, but each man must walk the path. Those who walk the path find walk the path find secrets that others miss.