Very high compression artifacts at 100% quality?

[metroidmen]

Even without FX upscaling, setting max HEVC quality to 100% the result is SUPER compressed and blocky, it is virtually unwatchable, in my opinion.

For reference, the result is 7.7gb for a 1:32 long movie.

Is this normal or expected results? Or is this a bug? I attached some images for reference.