Metal also leverages the neural engine. It's transparent, of course. I can't find the reference but it may have been one of the original Metal Apple Developer

Metal also leverages the neural engine. It's transparent, of course. I can't find the reference but it may have been one of the original Metal Apple Developer Conference (ADC) sessions where they let that slip. Of course other frameworks could leverage it too. As for direct access, I'm not sure. I think I did mix up API and framework in my response :)