I've tried this solution with a Samsung LCD, about a year old. I got only full volume audio from the extractor. I've used 2 different extractors and these weren't cheap. Both were from the brand Marmitek.
The Samsung was a 43RU7100. It was a very unstable setup. I've fiddled for hours. The idea was to connect a set of BL6000's via the extractor to the Samsung. But I ended up with an extra BM6500. Not the best idea I had in mind.
So, I assume that it differs from brand to brand. It seems after a lot of reading that every brand has it's own thought which sound they put through the extractor. There are examples that the sound of the tv itself goes through the extractor, but sound from some apps don't, like Netflix or Spotify.
Location: Utrecht