The key point some people are missing here is that removing noise from a video before compression makes it more compressible. So if you compare a video compressed without denoising/degrading at bitrate X to a video that was filtered and then compressed at bitrate X with "fake noise" added later, then the latter will have edges and details that the former doesn't.
The principle of post-processing videos to add noise or sharpening is something that desktop media players have supported for years, some are even reasonably good at it.
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