Real grain varies in intensity from scene to scene, or even shot to shot depending on lighting, lenses etc. It can also look like noise when scanned to video. Removing real grain, then adding some fake grain back in gives a more even, consistent look, while giving the image a bit of texture as a...
Film prints aren’t as sharp as digital, even 2K digital. They’re up to four generations removed from the negative and the mechanics of film projection further reduce the perceived sharpness. Even 70mm is going to fall short of 4K in projection.
I think that’s true and probably why I have somewhat mixed feelings about 4K, and particularly HDR. I find myself frequently preferring blu-ray over 4K as it can just feel more like watching a print.
I’ve always thought of it as the equivalent of reading a book translated from another language. It’s never going to be the same as the original, but there are translations that more closely capture the spirit and tone of the original.
There are a bunch of filmmakers - Cameron, Lucas, Zemeckis, Peter Jackson and, weirdly, Ang Lee - who same to have gone down this digital rabbit hole where they seem more interested in technology than in making movies, and the movies they do make feel more like vehicles to push the tech forward.
I don't think this has much to do with standard industry practice. In this case, as well as other recent examples like Picnic at Hanging Rock and American Graffiti, it's just how the director wants it to look. Or more specifically, how they want it to look now.