unless it's just because the manufacturer of those discs was producing better pressings.
bingo, got in one. give the man a prize. the late Jap laserdiscs basically kicked the crap out of a lot of north american stuff, even better than PAL, even though pal had higher res and color fidelity.
the more I think about this, the more I'm convinced the way to get a good color rich capture is off a PAL pressing because NTSC is known for poor color fidelity and inconsistency across frames anyway. it's not known as Not Twice Same Color for nothing.
also, no IVTC needed to get star wars back to 24fps film as PAL is only 24fps film speeded up 4% to get 25fps. just de-interlace, dot crawl fix and away we go.