The interactions between companies, no matter what the contract or tos states, are governed by law. Apple can’t build anything or run any aspect of their business without the government saying ok.

And government has often ruled that anticompetitive behavior violates antitrust law.

From the Sherman Act: “Every contract, combination in the form of trust or otherwise, or conspiracy, in restraint of trade or commerce among the several States, or with foreign nations, is declared to be illegal.”

If Apple is restraining trade (which they obviously are according to any reasonable interpretation, whether or not a court has yet ruled on it), they are breaking the law. Obviously the courts have failed us before and they take ages to rule on anything regardless, but I suspect Apple will lose in the long run.