

It’s main benefit is compatibility. As you said fsync is a hack and can cause issues with some games and applications.
The other benefit is more about packaging and the like, in that you won’t have to deal with third party patches. Not an issue if you’re using Proton but can be if you’re using vanilla Wine.
mpv supports Dolby vision (along with the Jellyfin clients that depend on it), but if you mean with streaming services, that’s unlikely to happen due to DRM.