> these communities don’t care if your code works at all, but instead care that you know why and how it works.

not literally true, and I doubt the author meant to say this. The communities do not only care about if your code works at all, but also that you know why and how.

It's sort of like in math classes where you need to show the work, not just the answer. Surely the answer being correct, while not being sufficient, is still necessary.