I mean this seems very reasonable from Apple's perspective. They're trying to avoid their brand being tarnished by bad repair shops with questionable repair skills cutting corners with cheap and unsupported parts. Given how large the resale market is for Apple products I would even say that this is an extremely positive policy because as long as the machine boots you can be pretty darn sure your MacBook is just like…
You mean like Nexus phones or Surface tablets shout out to the world on the boot screen that their bootloader is unlocked when you had the audacity to install a different OS?