This sounds like Claire going through the Scottish "Craigh na Dun" stones in "Outlander". As a guy with a Physics degree, I always ask "how would this be physically possible?" Other than a hiccup in a contrived, "Matrix" like reality (an actually rather good explanation of reality that has gained some science traction), perhaps either mass-delusional or glimpse of "many-worlds" reality (another growing explanation of reality).

I suppose the "rules" for "many-worlds" are that we are stuck in our own "world" (as the laws of physics prohibit "visits" from one to the other, by definition, otherwise the physical laws don't work). This is problematic for those wanting to "set foot" in both realities. However, there is nothing saying that you couldn't go back in time (simply a path in your own world, its just that you couldn't return?) Also, I wonder if there's ways to "see" other worlds without actually visiting them (this problematic too, since "seeing" also involves photons, etc from both worlds.

Sorry to dog pile on your fine article with this, but what if there's a "wall" between both worlds, like a drum skin separating the molecules inside and outside the drum? Maybe the "wall", like the drumskin, could be used to transmit information. Far-fetched, but perhaps the "retrocognition" people were somehow "seeing" the other world without actually being there. Perhaps if "many worlds" is true, there might someday be a tv-set window into other worlds?