Interesting article but the part where he says “all” you need to learn are matrix multiplications seems vacuously true to the point of meaninglessness. All numerical methods across every field essentially boil down to matrix multiplications.
Your math ability needs to be such that you can transform a problem into a form that can be computed numerically using matrix multiplications, which requires more skill (sometimes significantly more) than simply knowing how matrix multiplications work. Sometimes this ability to reframe complex problems numerically using matrix multiplications is the lions share of the research!