Interesting, looking at screen captures:
https://caps-a-holic.com/c.php?d1=18638&d2=18637&c=6775
The colour grading is improved and, interestingly, digital artefacts, such as edge enhancement, are eliminated...
I see no discernible difference in projected video quality, between Second Sight's 4K UHD and the previously released blu-rays, on three of their releases, which were filmed digitally: The Babadook, The VVitch and Drive. As you say, the extras are the bait for upgrading/double-dipping. I expect...