Took a bit of a break to rest my ears, but now I'm back at it.

I did listen to those raw recordings, and the surrounds can't be heard there either. But I think those are what Belbucus used to make the 70mm/1993 comparison track, so it's not surprising. Separating the comparison channels and playing them back individually, it seems quite clear that the theatre where the recording was made did not have an operational surround channel. The front channel portions of the '93 mix when folded down to mono seem to match up exactly with the recording, in the levels of certain surround effects that were also partially panned to the front, which really confirms my suspicion.

So while I still can't make any conclusions about the authenticity of those sounds, I'm leaning towards leaving them in simply because I can't prove that they don't belong there. There are a few places where the 70mm definitely added sounds that weren't in the stereo mix, so it's not unreasonable to think that these may be in the same category. With so many variations and sources used for later remixes, their presence or absence in those says nothing concrete about this version specifically.

Been going through the theatre recording with everything except the low frequencies muted, and while the bass is often indistinct and not of good quality, it does seem pretty similar to how they mixed it in 1993 for the most part, though not exact. I'll probably keep the LFE channel mostly the same as before, but I may change a few things based on what I'm hearing.