Why some audio streams on DVD-Audio disc are missing / not listed? How to extract from those streams?

For compatibility with DVD-Video players, some DVD-Audio discs could also come with a DVD-Video zone . When both DVD-Audio and DVD-Video contents exist on the same disc,  DVD Audio Extractor defaults to load the DVD-Audio zone, since that's what most people care about when it comes to audio extraction.

If some audio streams are not listed by default, most likely they exist on the DVD-Video zone. If you want to extract from the DVD-Video part, you could always select "Open from file folder..." and browse to VIDEO_TS folder of the disc.