How can you be sure it is legit? Like not converted to mp3 before being burned to DVD-A? Like this: FLAC torrent seed > WAV > MP3 > WAV > author DVD-A? You must be able to convert the .AOB files or .VOB files to WAV so you can do a spectral analysis, but I'm not sure how. Maybe it would be best to let people make their own DVD-As from FLAC seeds, especially if they are not going to make a menu or surround sound or anything fancy like that.

You don't have to convert your 16 bit files to 24 bit for DVD-A burning, I don't think Disc Welder is doing that for you. DVD-A can handle a variety of resolutions from 16/44.1 up to 24/192. You wouldn't be able to fit as much music on one DVD if you converted 16 to 24, and it wouldn't sound any better. You can fit about 7 hours worth of 16/44.1 on one DVD-A.