That is a reference to an earlier option I was suggested here:
My goal is to have a setup where I can watch content with the language pair of Japanese audio and English subtitles (common for anime) and English audio without subtitles (for most other content consumed). Currently I either have to disable English subtitles on everything else than Anime, or manually turn on subtitles and Japanese audio on anime that is dual audio (which is surprisingly common). I also want to be able to sync both of these content to my portable devices for consuming when commuting. Previously I also needed to Optimize the content for TV, since live transcoding was out of the question.
There are feature requests for more granular language selections, but I was trying to work with the system to make things happen.
