This article is really dense in its content and written with a lot of thought and thoroughness. I was struck by a couple of things, however, based on my own experience over many decades...

You wrote: "An enlightened mystic...might have a profound understanding of the act’s reality, one that views the act in a cosmic context that most of us can barely fathom" ...but "cannot explain how everything's really one."

This statement is not how I see it after having spent many years of enquiring into my own sense of self and coming to the point of this oneness. There are many other experiences that I have written about elsewhere. Unless one has actually done this enquiry to the end then all remains in theory and guessing what a person has actually experienced as reality.

I use the word "realization" to set it off from words like knowledge or understanding. Realization, as I use it, is to have grasped the reality of something at the deepest level. Even though a skydiver, to use your analogy, is skilled and experienced, she may still not grasp the physics, history, or full range of feelings from her experiences. So hands-on experience is not enough when it comes to this area of mysticism — a word that is also misunderstood and misinterpreted and interpreted per a person's knowledge and perspective. In fact, experience is transient and therefore not the irreducible fundamental reality.

The true mystic who has realized "the unity" can indeed explain exactly how everything is one. It is easy to do on many levels. But the explanation will not lead another to be fixed in this same realization. At best it MAY lead that other person to find it himself.

The mystic cannot convey the realization to anyone else, contrary to the claims of many devotees of personages such as Ramana Maharshi, etc. The feeling of oneness, if it occurs, becomes absolutely apparent in the same way that when you look at tree there is no denying what you are seeing. But it is not a vision, experience, or feeling and it is beyond knowing, knowledge, which is why the word realization seems to work better.

Truly enlightened (not a good word at all for several reasons) mystics — and I am not speaking of people like Tolle and his ilk — do not teach about the feeling of oneness. It is useless to do so. The realization of oneness is a byproduct of seeing past the egoic self, beliefs, ideas, ideals, a body-centric perspective, etc. The teaching must be about attachments and identities, and psychological condition that has led to the belief of separateness, that are obstructions to the realization of what one is beyond them. The mystic can only guide another person to find his/her own realization, because their words are no more than their own realization, and the word is not the thing.