So anything "requiring" a 4K release would almost certainly have had to have been up-scaled, unless the studio managed to get the original VFX vendor to re-render/comp and deliver 4K footage which I've heard of happening in a few cases (Star Wars re-releases, some Pixar stuff), but other than that isn't generally done and the VFX can only be upscaled from the "original" delivery.
The CGI could have done with a re-render, but the live shots might come out looking really bad trying to clean them up.
B5 obviously would have come out different as they would not have rushed to fit the planned storyline into season 4.
All those remastering are often done with more importance given to the economic side of things, instead of respecting the art.
Some are destroying the original work.
The first thing that pop into my mind is how they destroyed Buffy with the HD makeover:
https://www.youtube.com/watch?v=oZWNGq70Oyo
As a reddit commenter said about the cropping job: "All they had to do was nothing and they still fucked it up."
It's a disgrace.
And yet, they do. They throw away detail as they please. That’s preservation?
Compression is needed on torrent sites because few peers are interesting in downloading and seeding a 60+GB raw file of a movie if the 12GB mkv looks just as good on the 1080p Wallmart monitor.
There are of course also RAW rips of blu-rays out there but mostly for AAA IPs like Star Wars, LotR, Matrix, etc, not for niche content that have a reduced audience.
But "accuracy" is the wrong word I think, old home video transfers are not more representative of the original theatrical presentation just because they came out first
Denoising and Upscaling are both being done by AI these days, often in the same steps.
There is NO WAY that True Lies wouldn't support a 4K transfer. No way. Any 35mm print can be a great base for HD/4K, even one from the 1950s-60s, as shown by Criterion.
Unless you're talking about original 35mm negatives (which in some cases might have been lost / destroyed / degraded) where there is normally 4K resolution (with decent film stock - as mentioned before, some of the stock quality from the late 70s and 80s was very bad and digitising it didn't produce the resolution expected), using print copies (one or two removed from the original negative) will generally only give you 2K resolution.
The VFX would have been done at 2K anyway...
They are indeed forced to redo all the color timing by going back to the negative. And since they have the opportunity, they go “hey why don’t we just improve the grade”
Leading to a movie that looks completely different.
Somehow this also happened with the French Connection.
By the time True Lies came out home video already existed, so Hollywood had learnt about the long tail of movies in home release.
The kind of movies we don’t have good prints for are usually either obscure, so nobody wanted to pay to keep everything in good condition, or somehow damaged, or like you said, not good films stock or just old enough damage happened.
For its release on Ultra HD, Lightstorm, working with Park Road Post, has built a new 4K Digital Intermediate using recent 4K scans of the original camera negative (confirmed per Lightstorm). This footage has been “optimized” by Park Road’s proprietary deep-learning algorithms. Photochemical grain has been greatly reduced, though not eliminated entirely, while fine detail has been “enhanced” algorithmically. There are also occasional shots throughout the film that appear to have had a bit of old-school noise reduction applied, but it’s hard to be sure if it’s actual DNR or simply just that the Park Road process has been a little too heavy-handed in places.
Second, the restoration manages to bridge the gap between 1914 and 2014. Old B/W movies tend to give an impression of artificiality and distance. Seeing the colorized, interpolated version makes these soldiers people of blood and flesh. "This could happen to YOU", is what the movie says, and it couldn't have achieved it with the original footage. Given the slaughterhouse that was WWI, it seems entirely appropriate.
1. De-noising: often aggressive (and sometimes with pretty "basic" algorithms like bi-lateral filters) removal of noise / film grain.
2. Up-scaling. Note also that a lot of film stock in the 70s/80s was not that great quality, and even getting "useful" 2K resolution out of it might not always be possible (I'm not claiming that was the case in these cases, but it might be a consideration if a studio wants a 4K BluRay from the plate, which might not be possible otherwise)
3. Face replacements (Beatles Now and then footage only I think?).
They Will Not Grow Old was also colourised and retimed (the original footage like most 100 year footage was recorded by manually winding a handle to spool the film, so the speed of it (its frames per second) varies considerably leading to quite odd-looking footage (people walking is especially odd-looking) compared to footage we're used to within the last 70 years or so with mechanical/electronic winding.