I mean, in days of Android 4.x, Samsung wasn't able to not mess with core Android APIs for any release (and the bugs weren't even same across different models of the same darn phone).

My favorite bug in career is when we found out that OneUI (2? Don't remember the version exactly.) redefined @android:color/white resource. It was blue.

So anything that was set to white in your app was blue on that one model. That's the quality you can expect from the companies EU is trying to protect here. -_-

Requiring OEMs to be compatible with some Google-given (God-given?) Android version is a constraint on their business and their users. The point of EU's ruling is to allow incompatibilities to flourish. Let each user pick the best Android flavor they want.