OK understood now I think.
4) The audio channels are there as conduits for the audio and do not define the type of multi channel encoding used. The same audio channels here discussed can be used for a variety of different encoding systems, however, the decoding algorithm must be supported by the 861 for the audio to be delivered correctly to the speakers.
Did I get this right?
Not quite. With LPCM discrete channels, there is no encoding/decoding of various Dolby type formats. It’s pure SPDIF. The 861 does ZERO decoding. It reads stereo SPDIF pairs, and outputs the channels as defined. In this scenario, all the 861 DSP capability is used for upsampling/apodizing, room correction, et al…
The decoding MUST happen within the source device. In the case of ARC/eARC, it’s possible that the TV does decoding, but more likely it’s the source device (BR player, XBox, ATV, etc, …).