Any DVD gurus? While I do understand, why do we add CSS-protected discs decrypted, what's about other schemes? What's about bad sectors-based ones? What's about the ones with the modified UDF system? http://redump.org/disc/51036/ -- an example of the latter one.

It's always been encrypted DVD-Video into redump. That's how the guides have always specified them too. DVD Decrypter was just used as a mechanism to check if the disc had protection. Now that DIC/DICUI supports properly dumping them this should be less ambiguous, only accept discs dumped with DIC/DICUI for DVD-Video.