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Yes, that's part of the AV1 specs actually. See https://norkin.org/pdf/DCC_2018_AV1_film_grain.pdf

Andrey (who works for Netflix) drove the effort. Chatted with him about it.

I used to do a poor-mans version of that with low-bitrate mpeg4 (ASF or divX) movie downloads back in the day; the resolution would be low, and the MS MP4 codec tended to blur as well (plus noise killed the quality so much that there was often a denoiser in the encode pipeline), so adding any noise to the playback significantly improved the look of the movie.

Removing Grain and then re-adding it after encoding isn't specific to Netflix or even AV1 as some have suggested. I believe a recent part of H.265 HEVC, or H.266 VVC or MPEG-5 has something similar.