Re: How about..
Question, do you think macos/ios decode the audio then encode with a shitty bluetooth codec? No. For music they will send over the raw AAC stream and let the headphones decode it, i.e. no loss of quality beyond the lossy compression used in the first place.
The in ear AirPods do not have great quality, although they are reasonable, because they are fucking small, nothing to do with bluetooth, simple physics. These are not in ear though, they are not as easy to lose as they sit on your fucking head.