Interesting find! Not sure how someone could extract the original narration cleanly from a mono track though.
Maybe George liked the 1976 trailer?
Well, it’s not the same narration, I don’t even think its the same voice, it’s just done in the same style.
Maybe Lucas did like the trailer, after all the whole “somewhere in space this might be all happening now” was probably written before he added “A long time ago…” to the opening of the film, so he could have commissioned a similar trailer to be made but with updated lines.
It just weirds me out because its such a fan trailer thing to do, and I can’t imagine too many would have recognized the gimmick pre-internet. Then again I wasn’t even born in 1980 so I don’t know how familiar fans were with the specifics of trailers, maybe the 1976 trailer was considered a “classic” even then. I suppose Lucas could have just liked the vibe of it and decided to make a similar one for ESB before deciding to go with the other trailers.