Looks like they’re definitely from the included blu-ray, and not the 4K UHD, according to this italicized note in the review proper.

The included screenshots are sourced from the included 1080p Blu-ray disc, which has itself received a fairly drastic makeover compared to the 2011 20th Century Fox release.

So if I’m reading that right, EVERY screencap on that site for that review of Star Wars: A New Hope is taken from the '19 transfer that’s on the blu-ray, and not the UHD.

Hopefully they do that for the rest of the OT and PT, too!

here’s a quick side-by-side using their own screencaps
http://www.framecompare.com/image-compare/screenshotcomparison/9JBBCNNU