But then the rest of his article is precisely about how they're relevant. For example he says he doesn't care about type systems, and then his only code example

But then the rest of his article is precisely about how they're relevant. For example he says he doesn't care about type systems, and then his only code example is showing off Julia's type-specialization feature. Maybe he just means he doesn't care about the theory behind why it works, e.g. he likes to fly on planes but doesn't care to learn aerospace engineering himself (which is fine).