Why is it that so many magical organizations insist on having a secret inner order? Allow me to explain:
I believe the Gruntbuggly of Floop is a Grommit scuttle to Dupleberry, and it is why you cannot Narfle the wopping Thrusset while Frapping. However, Bob The Mad believed (as do I) that the Wallingford of Strine can help us napple the wibbly that mangles our Tinklewood and Stooples us to the Dupleberry, so that the divine Froppet can pinklefurl, and that if only a few Turlingdrone, then all will be able to follow.
I would be very worried if anyone could make sense of the above. However, to someone who has not studied the Golden Dawn at length, that is how a typical discussion might sound. In fact for the paragraph above, I took a typical belief and translated nouns and verbs into something almost as unintelligable to an outsider as the Golden Dawn :>.
I believe there is an event horizon in one's magical studies, beyond which it is not really prudent to discuss in open public forums key concepts, processes and ideas that one encounters. People talk about such things being dangerous, and the reason why such things are 'oathbound' in certain wiccan traditions. Personally, I do not believe such knowledge is dangerous in the literal physical sense. I do believe, however that premature exposure to an idea or concept that you haven't arrived at yourself can, in a lot of cases (although not all) lead one to misinterpret, corrupt or abandon their own magickal training or spiritual journey.
I might add I am not 'in' an inner order, but I have been and continue to be part of groups that have compartmentalization of ideas, simply because it is beneficial to the student to learn one set of ideas first, so that they can use those ideas to better understand other ones. Schools and Colleges do the same thing. That's why you have beginner (or 101) classes and not just advanced classes.
It is often stated that inner orders represent some kind of wierd religious sect, the outer circles of which are merely training grounds to find suitable individuals either bring in to the inner fold, or to manipulate for one's own ends.
There are sometimes groups like this, but you can easily spot them (and avoid them), since they tend involve you investing quite a lot of money and personal property, in order to obtain a seat on some intergalactic DC-8.
Usually though, I think you will find that any inner order is simply a study group of like minded, like-experienced individuals that share concepts and and ideas based on a common philosophical and spritual belief system.
An inner order has validity to the group itself, and to it's outer order students, the same as any organization. But there is no single bona fide not-valid-without-this-holographic-label inner order. The Golden Dawn for example, in it's Neophyte through Portal training (all of which is publically available), provides a wonderful system of training in both ceremonial magic and spritiual alchemy that can serve as a foundation for all manner of inner order studies.
Where that takes you next is up to you.