Indeed, we did previously discuss this, with screenshots. I'm still not seeing the huge difference you do, but this isn't a thread about that movie so I'll let it go.
As for Rules of the Game, I have a hard time understanding the point of a UHD release given the condition of the surviving elements.
Which Blu-ray editions did you compare it to? Believe me, I am very familiar with that film. The UHD is barely distinguishable from the Universal Blu-ray released in 2010.