That's a bit like saying that a physicist is more like to understand how a car works than anyone else because they understand all the principles of an internal

That's a bit like saying that a physicist is more like to understand how a car works than anyone else because they understand all the principles of an internal combustion engine. And yet, curiously, when we take our car to the garage the person fixing it does not tend to have a physics degree. Wanna guess why? I'm too tired now to expand the argument properly but basically understanding the components of a complex system doesn't mean you understand the principles of the system. A mathematician who is not an expert in AI has no reason to be particularly capable of understanding how AI works, i.e. how all the maths that go into creating an AI system come together to create. An AI system.