I'm curious about this too.
I myself have an Xperia XZ (F8331), with Android 8.0.0 (after it installed 7+ updates instead of just 1). My phone mic won't work in-call (received or sent) except when I turn on the speaker phone. Other audio like video recording , or the official Sony Audio Recorder app works fine. Even doing the diagnostic test worked. However booting into Safe Mode didn't work. Now most Sony Support people and customer service people say to Software Repair it. Big mistake as it doesn't work. So what's the problem? Better yet what's the solution ? (and no not some generic response that Sony Support usually gives). To weed out any pointless 'solutions': I have also disavowed/disabled Google Assistant and other Google Apps/ Permissions that require the mic (Android's biggest problem is the fact it's a Google product, also meaning aside from compatibility complications like this, there's TONS of bloatware). If this is a defect of Sony or even Google , why hasn't anyone (or can we even) do a class action lawsuit ? I just got this phone. I really don't want to replace it (especially since I did manage to somehow get it to work once, tho it was really quiet and stopped working ). So any actual help would be appreciated.
***UPDATE ***
I did some testing , and again, it works perfectly fine if the on speaker phone. Then I tried regular, again...not working . HOWEVER ... If I tapped it on something I could hear it on the other end, faintly . I also could FAINTLY hear audio (I had it placed in front of my PlayStation soundbar for optimum sound and controlled loudness). So it's definitely not hardware . It's almost like something is like capping it's maximum receiving amount.
***UPDATE ***
