Actually, the original mix was Dolby Stereo. Mono came up while discussing the isolated score on the Pioneer CLV disc, and the tradeoff between the LD version not being compressed, but being analog mono (one channel of the analog track), and the original DVD being digital and stereo, but 192kbps.
At this point, I think the stereo trumps the compression. The music was mixed in stereo, so a definitive presentation should have an isolated track in stereo too.