In your first link one of the comments says:

Die Lösung müsste eigentlich mit Hilfe des Buches zu finden sein (..who worthily will hear or read this book..)

And there’s another one that says:

jeweils 32 zahlen pro reihe. erste zeile seitenzahl zweite zeile wort? oder umgekehrt? wär mir als erstes in den sinn gekommen. leider gerade keine zeit das nachzuschauen.

So people have seen and proposed the method already in 2014 that it’s keyed to the book but had not had time to pursue a solution.

* Edit: Typo

Thank you, and SahAssar for doing the due diligence here. Like many others, I have at least a passing interest in cryptography, and I'm confident I'd never even heard of this before.

Is it wrong to presume they tried to run a similar prompt on all ciphers that come before this one in search results, and this was the only one that worked?

Which makes me wonder, other than the author and maybe two other humans on the earth, does anyone care about the cipher or the success?