There is no article since those screens come from various sources:
This mod is a collection of mods wich make the textures of the Witcher 3 not even just better, also tries to make every texture 4K resolution, more realistic and adds some exclusive custom textures.
www.nexusmods.com
New high resolution textures in 2K and 4K.
www.nexusmods.com
If you want to see it for yourself and have a decent PC then find a game with a 4k texture pack and load it up at 1080/1440p. Then go back to the lower resolution textures and look at how there is less clarity and detail in the overall image.
The point of reducing texture quality to suit the resolution is made By the Reddit thumbnail.
Look at it you have to stare and even then you can maybe see the difference, you have to increase the output area AKA increase the display resolution to see the differences.
seeing as 1440p is just under 70% of 4k and the 30% smaller disk space required for series
S is right in line with logic.
it's almost as if multiple software engineers with Ph.D.'s did the real math and came up with 30% smaller should be about correct.
as you mention going to 720 from 4k is a stark high contrast situation but there is also a difference going from 4k to 1440p.
it's measurable and according to Microsoft it might be 30%, Ms is just implementing the console doctrine of being efficient and authoring the solution/game to a specific spec.
Fewer pixels require less data to fill them
meaningfully, I think this is the only argument to be made.
the only question after that should be how much to reduce assets by if you are writing to accommodate a specific spec(Series S).