On a related note, why are release groups not putting out AV1 WEB-DLs? Most 4K stuff is h265 now but if AV1 is supplied without re-encoding surely that would be better?
I looked into this before, and the short answer is that release groups would be allowed to release in AV1, but the market seems to prefer H264 and H265 because of compatibility and release speed. Encoding AV1 to an archival quality takes too long, reduces playback compatibility, and doesn't save that much space.
There also are no scene rules for AV1, only for H265 [1]