That's Stage 1: Foundational Math -- with the addition of calculus-based probability/statistics, and the specification that it's the multivariable chain rule (not just the one in single-variable calculus), as well as differential multivariable calculus in general (gradient vector, etc.).

But there's plenty more to learn in stages 2/3/4 before you reach the cutting edge. Would encourage you to read the article! :)

Should also point out that -- in the USA, at least -- linear algebra, multivariable calc, and calculus-based probability/statistics are not typically taught in high school. There's quite a bit of university-level math that someone needs to know if they want to reach cutting-edge ML/AI.