Give me one single example of Apple changing the T&Cs and then retroactively removing Apps that are in violation of the new T&Cs.

Every single time Apple removed an App from the App Store is because the new version was somehow in breach of the T&Cs.

You could say that the rules was applied unfairly to Hey but nonetheless the T&Cs were clear as day about off platform signup/payments because it protects consumer from sham companies.