According to Lowry, they weren't recomped:
Whenever anyone lit up a lightsaber, it was done with an optical effect, and all of the opticals at the time were done on film--there were no digital effects. So every time you go to a lightsaber scene, bang, you drop two generations of film. It gets grainier and, as it's going through an optical printer, you have different characteristics in terms of contrast. And those are things we have to match up with the scenes immediately before and after. It took a lot of effort to match precisely the granularity, the contrast, and the sharpness. They flow very nicely now and, frankly, in the original movies, there was a distinct change. We were able to eliminate that change, and to me that's a very strong contribution to the storytelling process--removing something that prevents an audience from being drawn in.
However, Zombie reckons they were re-rotoscoped:
One unusual feature of this is the mention of lightsaber opticals losing generation quality--but these shouldn't be optical composites. In creating the 2004 DI, Lucasfilm re-rotoscoped all the lightsabers digitally from the looks of things, which would mean they went back to the raw negatives and not the final composites. Perhaps the negative in these scenes was simply dirtier because it had been run through the optical printer and picked up more wear. Videography says that they weren't actually using the O-neg but rather the 1997 Special Edition negative (the IN, I must presume?) because that was the only one that had the new visual effects work--but the O-neg would have had the new CG shots cut in, and why would they need to color correct it so heavily if it was the YCM Labs-corrected IN? Every other sources, including stills from their workings, and articles published by Lucasfilm (starwars.com) indicate that it was the O-neg, and not the the SE IN.
The 1997 SE seems to be identical to the 2004 DVD
We want you to be aware that we have no plans—now or in the future—to restore the earlier versions.
Sincerely, Lynne Hale email@example.com