Additionally some BD releases of Halloween and Mad Max have mono tracks that are actually downmixes of the surround track. The recent UHD release of Halloween sadly is one of them.
Yeah, don’t be fooled by studios simply claiming that the original tracks are included. Superman: The Movie is one of those where the first few BR releases claimed to have the theatrical stereo when it was really a fold-down of the modern remix.
Then there’s also the fact that a lot of times, when original mixes are provided, they’re in much lower quality (say, 192kbps AC3) compared to the modern remix (often lossless). Older laserdisc releases’ uncompressed PCM audio will often be superior, even if it’s the same mix.