Vero 4k+, LG CX, Apple TV 4k and Sonos Arc

As near as I can tell you are mistaken. I just tested it with a 7.1 TrueHD soundtrack and my AVR shows the input format as 3/2/.1 PCM being received with Kodi set for 5.1 channels and passthrough disabled.

This is also not correct. This question came up recently here…

According to the interwebs the Sonos Arcs with eARC and current firmware support 7.1 LPCM input.

I can, others can’t, some don’t care. Regardless, if one is going to bother tweaking their settings there really isn’t a point in using less than optimal settings.