However, like I said not all but some Netflix movies like "Limitless" do have audio encoded in Dolby Digital 5.1, but it will be decoded by the S780 and then output as uncompressed multi-channel PCM to your receiver.
Because its multi-channel PCM you will see PCM on your Receiver but you will not see "PCM 2.1" because its actually multi-channel PCM e.g. 5.1 surround sound. I know this sounds confusing since normally you would expect to see Dolby Digital light up on your Receiver but this is in fact the case with some devices when streaming Netflix videos.
When you can ...try streaming the movie "Limitless" from Netflix on your S780 and then really listen to your speakers --you'll hear the surround sound effect in each speaker.