I was talking about my combination of hardware, but I can do that with the integrated microphone in my MacBook and I'll hear the difference too. I can't comment much on Apple Bluetooth devices as Apple hides any codec information: they don't say which codecs and profiles are supported on their devices, and they've removed connection information in their OS, so I have no idea. But from what I've seen online, it's been problematic even for AirPods + Macbook users [0]
I haven't tested with any AirPods, and I don't know if they do non-standard things, but I've tested with a multitude of Bluetooth headsets and adapters, of different brands and supported codecs and all do the same thing.
This is because different codecs are only supported in the A2DP profile that's unidirectional. Once you use the microphone it needs to switch to the headset profile (HSP)or the hands-free profile (HFP).
HSP is very low quality in both directions, using a very low bitrate PCM encoding. Regular HFP is a bit better, also low bitrate PCM, 8khz sampling rate, but no good. HFP from version 1.6 supports a mono channel SBC encoded but in a 16khz sampling rate. Better but not great at all.
There's also a pair of codecs (FastStream, AptX LL) that support a duplex channel to send microphone audio back in good quality, but device support is not great.
And theoretically Bluetooth 5.2 with LE Audio supports Isochronous Channels, but I have no idea what hardware supports that.
So: Bluetooth audio is a mess. You need to mix and match a combination of standards and codec support in your computer hardware, your computer OS, your phone hardware, your phone OS, your headphones... quite a party.
I haven't tested with any AirPods, and I don't know if they do non-standard things, but I've tested with a multitude of Bluetooth headsets and adapters, of different brands and supported codecs and all do the same thing.
This is because different codecs are only supported in the A2DP profile that's unidirectional. Once you use the microphone it needs to switch to the headset profile (HSP)or the hands-free profile (HFP).
HSP is very low quality in both directions, using a very low bitrate PCM encoding. Regular HFP is a bit better, also low bitrate PCM, 8khz sampling rate, but no good. HFP from version 1.6 supports a mono channel SBC encoded but in a 16khz sampling rate. Better but not great at all.
There's also a pair of codecs (FastStream, AptX LL) that support a duplex channel to send microphone audio back in good quality, but device support is not great.
And theoretically Bluetooth 5.2 with LE Audio supports Isochronous Channels, but I have no idea what hardware supports that.
So: Bluetooth audio is a mess. You need to mix and match a combination of standards and codec support in your computer hardware, your computer OS, your phone hardware, your phone OS, your headphones... quite a party.