This is a very interesting and Iine of thought you have elucidated. Especially the distinction between Kensho
and what you refer to as the "'Expansive, I am God', 'Make me one with everything'" experience
I hadn't really ever considered that the two experiences were unique? For example, in some mystical experiences communication is experienced in a sort of timelessness without the usual linear coherency one is accustomed to, say like reading letters and words in context to derive meaning. Somehow the cognitive process appears
to derive information supra-rationally from disparate; logically disconnected sources. In other experiences people purport to be God?! In the specific circumstance I am referring to an individual is able to enter a plane of consciousness were his written statements seem to imply an different meaning than what is plainly written in the text - a form of double-entendre which seems to have a self-emphasizing quality which enhances the secondary or alternate meaning of the statement for those able to pick up on it. Moreover this individual has some very base conversational proclivities which disparage women while inflating their own sense of worth. In short the individual is megalomanical and their words are hypnogogic and sexually excitatory. These types of influential characteristics make the person not only a danger to themselves but to others (which is why I made the Manson and Koresh comparison) and so I was looking for some information wherewith I could reason with individual.
"Oneness" experiences are not uncommon. They seem like they should be wisdom. But there's still "I, me, mine" in them...even if that "I" seems to be the universe, "me" seems inseparable from "you", and "mine" appears to be everything everywhere.
Best case scenario: arriving at that place, which is not without merit, one can take the further crucial step which drops even this so-called universal self. A teacher is important here.
In other cases we end up with someone who doesn't take that further step, but is still relatively benign: universal oneness and a bigger perspective are not such bad things, actually, so at least some spiritual figures who have had this experience deeply might not do harm. They could benefit some folks. It's just not liberation from our standpoint.
Worst case: one gets stuck in it and uses it to rationalize/feed deluded tendencies. The result is a spoiled child whose playground has suddenly become the entire universe, and whose toys are all people and all things. Add to this some amount of natural charisma, energetic power and so on and voila: instant cult leader.
Lots of kensho experiences folks think they've had are actually not it at all. Lots of folks who've recognized their nature do not undertake or continue the important cultivation afterward to return to it again and again, deepen and refine it, and embody it: a truly difficult and lifelong training.