I know that’s what happens, but the bug is that it stays in that mode even after the VM has relinquished its claim on the microphone.
Note that this only started happening in this particular scenario after 10.14. It happens in other scenarios from time to time (that is, it stays in HSP even after the app requesting mic use is quit).
https://en.m.wikipedia.org/wiki/List_of_Bluetooth_profiles
It's likely switching from A2DP to HSP because the microphone is activated.
This is very common with Bluetooth headsets and it's what still makes me choose corded headsets to this day.
Newest Bluetooth reviews are supposed to have more bandwidth for high quality audio but I'm stuck with (not so) old speakers and car.
If you need wireless, it's better to go with one of those 2.4GHz receivers but they require a small USB adapter. Not really a solution for AirPods.