Does Bluetooth support binary transfer? Why can’t it be just a dumb wireless data transfer protocol. Instead you have profiles and lossy compression. Turn on a mic and the quality drops to phone quality 30 years ago.
Max bandwidth for regular Bluetooth is around 3 Mbit/s, to my knowledge. Bluetooth LE is lower at 2 Mbit/s.
https://www.novelbits.io/bluetooth-5-speed-maximum-throughpu...
In any event 300kbps is more than sufficient for transparent compression of audio and, if the source is lossless, then you shouldn't have recompression artifacts. Doing so in real-time does have costs (low latency compression uses both more CPU time and ends up with higher bitrates than when you allow more latency)
A funny thing I‘d do if I had more time and energy to dedicate to the topic of Bluetooth telephony (HSP and HFP are garbage for arbitrary reasons) would be opening a network and doing reasonable quality telephony over it to demonstrate it‘s possible.