If I understand correctly, in the real world where multitrack recordings are the norm, nearly all SACD and DSD-download releases have passed through:
(A) DSD-wide (Sonoma)
(B) 32/352.8 PCM/DXD (Pyramix)
(C) are converted from PCM sources varying from 20/88.2 to 24/192
(D) are sourced from two-track analog mastertapes
If that's so, then "pure" DSD recordings hardly exist at all, in the narrow audiophile sense of 2 microphones -> preamp -> ADC -> DSD -> DAC -> consumer playback. What we're hearing are either all-analog sources, dating from the Eighties or earlier, or more modern recordings which are sourced and mixed in studio-grade PCM, DXD/PCM, or DSD-wide.
Bruce, you're the professional, and know the answers here. What about recordings from the mid-Eighties to the early 2000's, before Pyramix and Sonoma? The 24-track tape machines and EMT reverbs were gradually replaced by all-digital systems, at fairly low PCM resolutions (20/44.1?) at first, then 24/88.2 and 24/96 by the mid-Nineties.
I'm guessing these recordings from this era might be partially analog, but have passed through at least one stage of PCM of varying quality. If the 24-track analog master still exists, the recording could always be re-mixed in a purist Sonoma environment, but if the multitrack master is PCM (on disk or tape), there has to be a transcoding step into the world of DSD-wide, then a reduction to DSD-narrow.
Is this a correct picture? You have one of the few studios that specialize in DSD, so you must know more about the origins of SACD and DSD-download recordings than most of us.