That's just a Bluetooth capacity problem. Bluetooth isn't built for high throughput scenarios and "HD bidirectional audio" is considered high throughput in this case.
Same problem happens with a combination of earbuds and a smart watch, or headphones and a Bluetooth mouse, depending on the interference and chattiness of your devices.
I'm not talking about anything HD, basic mouse keyboard via BT and simple SBC for the headset. Never had any issues with that combination on Windows in the past before jumping on to Mac 6+ years ago. To add insult on top, I still remember many people telling me to "just do" a full system reinstall to see if it solves the issue.
It depends on how chatty your mouse is. "Gaming" or "high-resolution" mice can spam the BT piconet and cause issues, but a basic office mouse will work without issues.
It definitely varies a good bit with the hardware in question, and even how saturated 2.4GHz is in your current environment.
I currently have a bluetooth mouse, a bluetooth keyboard, and bluetooth headphones all on the same device and haven't had any issues. On a different computer with a different bluetooth chipset it would have issues with audio when I moved my mouse around a lot.
Same problem happens with a combination of earbuds and a smart watch, or headphones and a Bluetooth mouse, depending on the interference and chattiness of your devices.