I found another example of a possible improvement here:
https://caps-a-holic.com/c.php?a=1&x=400&y=128&d1=18304&d2=18305&s1=212240&s2=212224&l=0&i=0&go=1

The lines on the bedspread, on Cinderella’s dress and in her hair, which are missing on the Blu-ray, are back on the UHD.

I can’t see much difference in the colour of the famous silver dress, which was dyed blue in later releases:
https://caps-a-holic.com/c.php?a=1&x=443&y=198&d1=18304&d2=18305&s1=212249&s2=212233&l=0&i=9&go=1

I searched the internet for Production Cels of this dress to see what the colour (and Cinderella’s hair) really looked like, and I think the UHD is pretty close to the original, especially with the hair.

However, I would be cautious not to get too excited, as it is possible that other scenes have been distorted by the use of colour filters or similar. Perhaps someone already has this UHD and can report on it? By the way, I’m not a fan of this film either, but if this release is really perfect and shows the film as it was made, then maybe there’s hope that the other Disney films will also get proper releases.