Since when Episode I was originally finished, it was done on a per shot basis - “done sort of old style, final a shot, film out a shot, look at a print of that negative and that’s what we would final”. It went through a conventional negative cut. An optical timed IP was generated from that and then then master printing negatives were made from that timed IP. So everything audiences saw in the theater was two generations down from the original. “When the original DVD was released,” Knoll says, "it came from scanning in the timed IP because it was the simplest thing to do.

A bit of info from here: https://www.fxguide.com/featured/art-of-stereo-conversion-2d-to-3d-2012/