Not sure if this contributes to the conversation but I’m gonna throw it to the air. I still have the terminator on vhs (recorded to dvd and then digital) and I noticed in the fullscreen version that the aspect ratio has a lot more headroom. When the “T” and “R” in “Terminator” cross at the beginning of the opening credits, you can actually see the top of the letters slide across each other, and THAT’S why you hear that metal scrapping noise. Not sure if the entire presentation has that extra headroom though, as it might just be only that part.
I’ve been made aware of the origin of the sound effect before, and I find it interesting that they framed it to be cut off like that. I would assume that the whole film is open matte, though it’s definitely possible that some of the optical effects shots were hardmatted. I actually have an old HBO Video VHS that I watched once, but I don’t remember what the framing looked like.