Little background - I'm about as secular a person as you'll meet, I also came into pu'er rolling my eyes into the back of my head whenever I heard a comparison between qi and cannabis or opioid-like effects. I figured it was coming from people with limited-to-no experience of either. I don't meditate, though I do have some small experience "leaning into" psychoactive effects and making the most of chemically-altered states.
I held onto that for about nine months before I was forced to admit the potential for legit psychoactive/physiological effects from teas. Whether or not you attribute it to mystical forces, it's hard to ignore it when you start sweating bullets, or feeling a comfortable (and yes, broadly opioid-like) floaty feeling in your head, or feeling your skin "buzzing" all over, or a growing feeling of mental clarity. It's very inconsistent, very personal, and often something you have to "lean into" the way you might have to lean into a low dose of a psychedelic, but it's certainly real in the sense that some people experience effects that they probably couldn't talk themselves into.
To quote (I wanna say) Hobbes, pu'er is drugs.
The reason it seems mystical for me as opposed to a sort of commonplace drug-like high is the feeling of oneness with nature that certain teas can bring. This puts it inline with psychedelics more than something like alcohol because of how it can be quite fulfilling and deep. I'll cite the title of the deadleaves article "sip straight to the soul"