I was initially skeptical, but this looks pretty solid after reading. The author seems to be an absolute beast though, so anyone diving into this should expect to focus and work hard / very consistently.
Most anyone can learn how to write code, however adding different skills can increase both the quality of what you produce, and the breadth of problems you can solve. You don't "need" to learn things like program complexity, but knowing it can help you write more efficient programs; you don't need to know math, but it helps if you want to work with encryption, and in a way testing, too.
What does that all boil down to? Probably curiosity, practically speaking. If you're genuinely interested in programming, and it's not just about money, status or proving some point, you'll be drawn to learn different things and have different discussions, over the whole course of your career, that will make you a good programmer, rather than just a passible coder.