The computer knows what it's sending to Bluetooth and it knows some model identifiers from Bluetooth. This could be implemented well. But I agree, it probably isn't.
What if the manufacturer changes the sensitivity but keeps the Bluetooth identifier the same? I assume Apple would rather set a conservative limit for everything than risk getting sued for allowing hearing damage with an incorrect custom limit.
If not raising an alert is "allowing hearing damage" then they already do plenty of that, as does everyone else. It's not a reason to do a poor job. Maybe an excuse, but not a reason.
It'd have to set up their own audiolab and produce a long list of models and what the output levels are per volume setting. OTOH, these things should be standardized.
