Note: This was originally a submission to Google Pixel Buds support.
Community Post: https://support.google.com/googlepixelbuds/thread/190008139?hl=en
The Issue
Hello, I’m having the issue faced in this thread
Essentially when using Windows 10 and the Google Pixel Buds Pro over Bluetooth you’re presented with two device options Hands-Free AG Audio or Stereo Device.

You must select Hands-Free AG Audio to use the microphone, not the Stereo Device. Unfortunately, the audio quality using the Hands-Free AG Audio (Headset) is extremely low quality for playing music.
This article from 2018 talks about the issues faced with using a Bluetooth audio device with a microphone. https://www.howtogeek.com/354321/why-bluetooth-headsets-are-terrible-on-windows-pcs/
Then there is this thread on superuser.com, which goes in-depth about codecs and Bluetooth headsets.
https://superuser.com/questions/1678340/possible-to-use-bluetooth-5-0-headset-in-high-quality-stereo-mode-with-mic-simul
So, it seems impossible to use the Google Pixel Buds Pro microphone while also utilizing the stereo quality sound because AAC and SBC don’t support this AptX would have.
The Verdict?
Look for an AptX compatible device.