I just recently found out the hard way--after screwing up a bunch of albums--that using ffmpeg to concatenate multiple 24 bit files into a single one results in the output file being 16 bit. In fact, it was while researching how many I'd ruined that I discovered this issue with the Parsons disc.
I'm still furious about ffmpeg--I had started using it to get used to it in case SoX, which hasn't been updated in years--goes away. If you tell SoX to concatenate, the output is the same as the input (because why on earth wouldn't it be?), but ffmpeg does its own thing.
I mention it because a lot of the Linux audio processing code seems to be shared and copied amongst different applications (e.g., you can tell ffmpeg to resample using SoX's resampling library), so I suspect you're onto something. Still, it's odd that this is the only disc any of us have encountered that shows this issue.