The first main problem with Bluetooth is that channel speed didn't improve since Bluetooth 2.0 + EDR (circa 2004). While the Bluetooth 3.0 + HS allows to use AMP (Alternative MAC/PHY) to improve speed, this feature is not used in mobile devices due to the high power consumption. Did you ever see +HS suffix on any of your devices?
Bluetooth 4.0 + LE was an attempt to reduce power over WiFi PHY, Huawei Y6 2018 support it, but even the latest headphones do not support for BLE. Something is lost in woods of profiles...
Bluetooth 5 (supported by Mate 20) is finally focusing on IoT, but it seems there is still a dilemma of chosing a range on expense of speed and in reverse.
These tests show that Bluetooth is still not suitable for hires audio: https://www.soundguys.com/ultimate-guide-to-bluetooth-headphones-20019/
I walked through all graphs and came to the conclusion that Bluetooth transmission channel is not transparent. In theory if a device support a codec of the source material and transmission channel allows to pass it through unchanged, there should be no further transcoding. I blindly assumed it would work that way. In practice it doesn't and it is really stupid.