Their solution -- which worked -- was to turn off the AirPods microphone. Reporting in a few months later and I'm still facing issues with this. I'm running the release edition of macOS Big Sur and I've noticed that my AirPods Pro Bluetooth quality also drops when I open the "Bluetooth" settings page within System Preferences. In macOS Catalina, a user could view the current Bluetooth codec in use by holding down the option key and clicking on the Bluetooth icon in the menu bar. However, they removed this feature in the Big Sur redesign. I'm very frustrated with this, because now there's no easy way to see which audio codec is in use by the AirPods.

I'm running the public version of macOS Big Sur (11.2.3 (20D91)) and I've noticed that my AirPods Pro Bluetooth quality also drops when I open the "Bluetooth" settings page within System Preferences. In macOS Catalina, a user could view the current Bluetooth codec in use by holding down the option key and clicking on the Bluetooth icon in the menu bar. However, they removed this feature in the Big Sur redesign. I'm very frustrated that they removed it, because now there's no easy way to see which audio codec is in use by the AirPods.