You ranting about "old" vs "new" will not solve your problems, instead you are just wasting other people's time trying to figure out your issues. And after I explained it clearly to you, you will immediately know whether people that are helping you are BSing or not.
This is a "budget" vs "premium" audio packages issue. You need "speaker fill" to play stereo music or youtube videos in all 5 speakers. "Speaker fill" was deleted in your realtek audio console because you have a premium DTS audio package. But DTS doesn't give you that feature.
The most recent ASUS/DTS discussions --- even the asus forum mod doesn't really understand the issue and is now complete radio silence.
https://rog-forum.asus.com/t5/amd-600-series/tuf-gaming-b650-plus-speaker-fill-missing/td-p/932299
Nothing to do with "old" vs "new". It has been like this for over 10 years --- features got deleted in the realtek hd audio manager and moved to the premium audio app.
My "budget" computer has speaker fill in the Realtek Audio Console.