I hope you don't mind me joining in the conversation at this point.
Are most of those classical SACDs being issued in multi-ch or primarily stereo? multi-channel.
prestoclassical.com currently has 3,934 different multi-channel SACD's in their inventory.
Is it the supposed higher quality that keeps 2ch classical SACDs flowing? Classical SACD's are released in multi-channel. There really aren't 2 channel classical SACD's out there (at least I've never run across any). The only 2 channel SACD's I have in my collection are rock CD's that have been remastered and released as SACD. The "supposed" higher quality and remastering is what is keeping companies like Mobile Fidelity in the SACD market.
At least I don't get a majority of classical SACDs when I search a catalog by "multi-channel SACD" try this link to prestoclassical.com:
https://www.prestomusic.com/classical/formats/sacd/browse
That seems a crowd that often poopoohs multich audio nor uses multi-channel gear. That is true for many, possibly the majority of classical music listeners. But there are enough classical listeners out there with muli-channel systems to keep many labels in the SACD game.