Why can't I see the audio my Sonos Arc is receiving in the S2 controller app?

My Sonos surround system (Arc+One speakers+sub) is at present receiving its audio from a 2011 55-inch Samsung TV’s HDMI (ARC) port. The app does not show the audio format on the TV’s “room screen.” When I go to “About my system/Sonos System info/Sonos Arc: Family Room,” the “Audio in:” always shows “stereo,” even when it sounds like I’m hearing surround sound. So, to my questions: why doesn’t the app’s room screen tell me anything about what audio signal the Arc’s receiving; and why does the “Audio in:” come up as “stereo” when the system sounds to me like it’s putting out 5.1 surround sound? Is the latter possible because (1) my 9-year-old Samsung’s HDMI ARC doesn’t support 5.1 surround and (2) the Arc and the surrounds are going a passable job of simulating it? (The Samsung’s optical audio output only supports PCM.)

My issues with the app are are short term--I hope--because in a little over two weeks my Arc will be receiving its audio from a 2020 Sony X950H TV with an HDMI eARC port and passthrough support for Dolby Atmos, DTS, etc., etc. But in the meantime, I’d like to get some answers to the questions above.