There is also the issue that the dynamics and EQ settings were not automated on those consoles. They still relied on engineers marking their settings by hand on template sheets for each track. I wonder how many of those were archived with the multi-tracks?
I'd really love to get some insight into how Steven Wilson makes his decisions. Is it all by ear? If so, then much respect!
A lot of what the famous mastering engineers did was purposely undocumented for trade secret / job security reasons. One of the biggest appeals of "original pressings / first pressings" is that a skilled mastering engineer like Robert Ludwig worked with the artists to tweak the master tape recording to "sound better" as well as adapt it to the limitations of vinyl. Even later versions of the same vinyl record can sound different as after the original stampers wore out the replacement stampers were mastered by someone else. Going back to tapes with cryptic notes decades later to transfer to CD's it is not surprising that they often sound different.... which is not to say that they don't sound closer to what is on the master tape. Personally I usually like to hear what the original sounded like even if not perfect.... it's not like the remasters are perfect either.
Here is an interesting story about Steven Wilson's approach https://www.soundonsound.com/people/steven-wilson-remixing-classic-albums