IIRC Android uses a regular Linux Bluetooth stack.
Also WRT your problems: In case you did not yet, switch to Pipewire. When I did that a couple of years ago, my BT Audio experience went from bad to really good.
It can be very device dependent, or even on which mode the device is in dependent.
For example, I have JBL headphones, that work perfectly in the A2DP mode; but switch to HFC for the mic, they will work for a few minutes, then drop off and stay that way until reboot.
That's with Ubuntu. With Android, no such problem.
Also WRT your problems: In case you did not yet, switch to Pipewire. When I did that a couple of years ago, my BT Audio experience went from bad to really good.