AirPods: Does the H1 chip use a proprietary bluetooth profile?

Question

The AirPods don't seem to use HFP (only 16Khz) nor A2DP (output only) when talking with Apple hardware (iPhone, Mac Book). I noticed that when calling in Discord or Skype on my iPhone the audio quality remains surprisingly good, which seems to be impossible with the standard profiles AFAICT. It's clear to me that they need some sort of protocol for controlling the AirPods ANC settings (etc), but I wonder if that same protocol is used for audio transmission?