Your argument is equivalent to criticizing ARM for putting in instructions to optimize Javascript into their architecture, as if that "sabotages" every other programming language. Or Intel for putting in instructions to optimize AES into their architecture, as if that "sabotages" Salsa20.

It doesn't make any sense. Of course Apple optimizes Metal for their GPUs and their GPUs for Metal. None of that is hostile towards other APIs. All of this hardware is Turing-complete and by definition can implement any conceivable graphics API. The only question is how well it performs with those APIs, and until we have benchmark numbers, your argument is based on assumptions lacking any evidence.