Just saw this screengrab of the 4k version. Bad news. It looks the same colour grading as the 2004/2011 versions. Vaders green lights are Blue in those versions yet fine in the 97 version. If they do have the exact same grading problems that have only ever been present in the versions taken from the 2k master done for the DVD’s/ Blu-rays then these aren’t new transfers, just upscales
ROTJ is the one that we’ll be able to tell for sure if they are new transfers or just upscales. If that film still has the “out of focus” scanning problems as they approach Endor, right up to the speeder bike chance, then they are the same 2004 masters
I read a comment elsewhere that that scene has been fixed.