Sorry, I didn't mean to comment on your expertise, but rather the epistemology of who we believe.
> My knowledge comes from someone who helped develop Dolby Digital on film so I'm pretty sure it's correct.
That is certainly better information than anyone else here has, and you seem to actually understand the technology. I wish HN was 90% comments like yours and almost none of the rest, especially Wikipedia!
But while we're talking about epistemology! Decades-old memories go wrong, and when vested interests are involved the memories can drift to desired beliefs or familiar narratives. That doesn't make the comment a bad one - it's very valuable, actual knowledge. But it's not sure to be correct either, and/or not precise.
Absolutely true and I agree with you. Something else to back up that it's not quite AC3 is that I've captured the raw signal that goes into the decoder box's "AC3-decoding card", and it's not quite what I'd expect for AC3. You can learn more about that and download the raw signal capture at https://fanrestore.com/thread-2633-post-73179.html#pid73179
Holy cow, what an amazing-looking community! What is going on there? Who is behind it? And when people restore a work, can they share it with other members?
I suppose he could get away with nobody adding the [citation needed], but that'd be against the rules.