Chiming in here because I add physical releases and am intentional about the mastering SIDs and mould SIDs. My two cents is that we should allow for multiple SIDs per release, whether or not that’s accomplished with the “variants” idea proposed here. I’ll note that the “variants” section on Discogs releases is often incomplete and could potentially never practically be complete (for many releases).
I’ve encountered many releases lately with differing SIDs (e.g. Edit #79818764 - Remove relationship (Edit #79818764 - MusicBrainz)) that should probably be handled in a better way than adding a new release for each SID.
Furthermore, I’ve encountered CDs which date/time stamp the matrix/runout (e.g. https://www.discogs.com/Aphex-Twin-Syro/release/6112678) which would generally imply that every individual CD deserves its own release (clearly impractical).
I wish I had more answers than questions, but at this stage I’m still working to read through and understand the historical perspective and conversation as to not fall into the same traps we’ve already hammered out.