I like to think anything is possible- but due to the lack of evidence I find myself hard pressed to believe that you can experience the plunge through hyperspace- along with all the content: the EXPERIENCE/learning/revelations/growth and knowledge of yourself and the cosmos that comes along with it- without taking a psychedelic.
For instance I've lost all sense of my body as it dissolved into the impossible alien landscape of unfathomable complexity and I was no longer "ME" but all of "IT"; the 'beings' the geometry, the machines, ect of this place "i" used to be in, but now was. This type of revelation that humans being can experience their dissolution and apparent becoming of something else entirely is baffling and I can't imagine it occurring quite like that without a psychedelic. I don't know if this should be classified as knowledge at all, delusional or not, or attainable by other means, but to me it doesn't matter much as its just another unexplainable conundrum of human experience added to mounting pile.
That isn't to say that you can't have a realization in sober life that you would have come to earlier had you taken a psychedelic. I'm sure many people along with myself have had realizations about themselves or the universe that came to them during sober life, and later had similar or seemingly the same realizations during a trip, or know others who had the "same" realizations in sober or psychedelic states as they had.. But this is completely different from having the SAME EXPERIENCE. The unfolding of information in ones life (also the content itself), its lasting impact, and experience in general, is going to be different every time, to everyone, no matter how apparently similar the infos meaning is.. A lot more comes along with the unfolding of knowledge gained through experience and the impact that has on a person than just the short-cut-and-dried five sentence description of it on a piece of paper, which, although across experiences may appear to be the same in writing, is really much different to the life of a living, breathing, universe experiencing human with a brain flowing through time.
So you can say that people could have came to the "same" realizations about themselves by other means but I think the experience -and the seemingly identical realizations themselves- are going to be different every time, for everyone, and especially so in psychedelic states; which will inevitably lead to different outcomes. Maybe that is why some alcoholics have the realization that they are killing themselves in normal life and it doesn't have much impact, then had it again during a trip and it drastically altered the course of their life. So maybe its not right at all to call information learned through one experience the "same" as other possible experiences of ways to obtain it since no experience is EVER going to be exactly the same and thats what realizations, or the unfolding of information in life is- its an experience. i hope this ramble makes some sense