I ponder in particular what he means by "disregarded". It did not seem as though Shin Ankoku outright retconned this out of continuity, did it...?
They probably just meant it wasn't mentioned at all, hence "disregarded".
there's a lot of references to playing of the OSV versions of Monshou no Nazo when all the music I heard in this was arranged or at least slightly remixed. Someone who cares to do some translation work might want to check me on that though.
I haven't read the transcripts in depth, but I'm assuming they just used the OST as a reference, since it (or its tracklist) is both official and widely available.