The product and release date of this album might need a bit of examination.
I think this album was for Darius Plus (one of the PCE ports), since Super Darius just used redbook audio and Isoda talks about the unique sound of the hardware's PCM (mini-wavetable) sound function on
the liner note. Hope somebody who can listen to this album confirms it.
As for the release date, some sites and
the back scan says it was Nov 5, 1989. With either date, it was a little too much ahead of the game's release date (Super Darius: March 1990, Darius Plus: September 1990) and that's also why I'm wondering... my common sense says it'd normally be November 1990.
EDIT:
This page explains lots!