Again check the codec mac is using for this. I've had no issues with them, you either had a defective device or Mac is forcing the SBC codec. On windows there's a headset audio device for every bluetooth device that sounds garbage too (regardless of what the device actually is).
There's no way to set the codec on the Mac unless the individual software has an option for it. Considering that no other devices have this issue and it was improved with a firmware update, I'm going to say it wasn't an issue with the Mac at all.
Again check the codec mac is using for this. I've had no issues with them, you either had a defective device or Mac is forcing the SBC codec. On windows there's a headset audio device for every bluetooth device that sounds garbage too (regardless of what the device actually is).