Yeah, not sure on audio quality. To my ears DVD audio is already in the realm of diminishing returns unless the mastering was done very poorly. No clue if they were doing 5.1 or any sort of multi channel on the DVD releases either.
The better quality because of more room for higher bitrate makes sense assuming they still have the final cuts pre-dvd-compression laying around. This could get you some crisper, less artifacty output.
But this is also just speculation on my part. I’ve never checked out one of these sd-bluray-re-releases myself.