I know you discounted my suggestion, but even the older linked systems were quite advanced.
The TV is capable of outputting different volume levels to connected speakers. The Beolink Converter is a very “powerful” piece of kit and I would say it might be reading those volume signals.
The user manual for your TV says that if you get SPEAKER up on the Beo4 and then choose 1 to 5 you will get differently speaker combinations playing (not all presets will work depending on your set up).
I can’t see any harm in trying it to see if any if the make a difference.
Stoobie.