Except it doesn't quite work like that. Many of Waite's secrets are amply put forth in his voluminous corpus. Mary Greer has spoken of them here in the past, and they are there for anyone to find, provided they are willing to find them scattered across 50+ books. That not many GD members revealed the orders secrets is a testament to how much those who did blab reveal. Between Crowley, Regardie and others, there's not much original GD material that still remains secret, if anything.
As for blinds, the few that are actually in the PKT are easily refuted in GD source material, and so lose their blindness.
When secret societies talk of, well, secrets, they're often referring to things that have to be experienced in order to be understood. The Golden Dawn wasn't a Tarot-making society, it was a semi-Masonic order dedicated to initiation into higher consciousness, magic, etc. I could list attributions and theoretical GD practices from here until the cows come home, but that still doesn't mean I have a grade or anything like that, because I am not a magician and do not spend my days in meditation and ritual. The knowledge has been passed on, but not everyone is willing or able to do the work. They don't call Regardie's book "The Complete Golden Dawn" for nothing. That, finally, is the "secret."
As for the book, from what I have seen it is completely subjective, and does not present anything "ultimate." It seems to be just like any other book about the RWS, except for the format, which is in "listicles," for people who read Buzzfeed.