The update did help.
Previously Tesla could be a Bluetooth desrination but not a source. i.e. you could stream to the Tesla but not stream from the Tesla to anything else.
Apparently having multiple audio destinations is new in Bluetooth 5: Curious if something similar is or could be implemented by Tesla.
But now that car has two internal sources, maybe they planned ahead. It would be handy to play the rear source on the whole car speakers and fade to the rear speakers.
As for getting the rear source on headphones in the back, is there any source out, wired or wireless? If the front MCU can get audio from the back, any clues as to how it is done? The headphones in the back request is legitimate. Someone on the forums will figure that out and hack a solution if Tesla didn’t. There are lots of third party solutions to leverage. I am less enthralled with wireless and keeping headsets charged so a wired solution like to those USB-C ports below the rear screen would be ideal for me. Even if it needed a goofy splitter, although I doubt those are wired for anything but power.