To write something you must form a "theory of the system", which is orders of magnitude more difficult than feeding on fodder. It's the difference between being fluent in a language and sort of understanding something.

It's quite similar in hard sciences as it's in natural languages. For instance I don't understand Hungarian at all. Few words "igen", "jó napot kívánok" doesn't a knowledge of the language form.

Then German. I had to learn it in school so I have orders of magnitude better grasp at it because I can actually say a few statements that form in my mind: "Nein, ich brauch nicht ein anderes stück Steak". Might not be 100% correct gramatically and vocabulary wise but it conveys the message and also transmits that I understand the context.

And then come English which I speak since 33 years. I actually THINK in English a lot of times and there are concepts I can't easily express in my native Romanian language without resorting to a painfully long and sometimes unsuccessful software-driven (as opposed to FPGA-encoded) translation process.