I’m not convinced. Complex numbers are a representation of a system. Yes, you can express it somehow else, but at its core it’s the same. As I understand it, they are saying that using complex numbers is the simplest (pun not intended) representation necessary and there’s no further simplification possible. That is meaningful because an ancient Greek would say that reals or even integers are sufficient to describe the world. They are not. Just like Euclides was not enough.