I don't think the part some refer to as mystery is the exact same as the parts I refer to as malarky - the malarky, to me, is the deliberate obfuscation and smoke and mirrors about what they do and how they blame and label clients who don't roll over and submit or who want more explanation than those guys want to give because it either exposes them as being dead flat charlatans; or someone who is just stabbing around and guessing and hoping; or someone who is trying to do something at or change the client in ways that the client does not want.
The mystery part, to me, is more like the religion or tinker bell part - where the client is expected, with no explanation or good reason, to simply believe really hard and take the leap. And for some it works. For others it ends very very badly.