The larger issue seems to be where there is calibration info that needs to be set up but only Apple has the software and tools for it.
You're assuming a technical, informed and assertive user here. There are lots of people who don't even try to turn off and on the phone when buying. Or fall for bullshit like 'it's normal, just ignore that message'. And what do you do when some repairman used a knockoff battery and is threatening with calling the police if you don't accept and pay for the 'repaired' phone?
Apple could put in as many oem checks as they want, hell, even throw a persistent warning in the settings menu or something to inform and even dissuade but they should absolutely allow it at the end of the day.