Because Writing forces sharper understanding, many thinkers will write an essay or a book in order to more deeply understand a topic. For similar reasons, writing questions in the mnemonic medium likely also helps writers understand their topic more deeply.
Writing effective questions requires you to develop clear theories about what’s important. It requires you to more formally structure knowledge that might have been more loosely represented in the prose. Because it readers will memorize the cards you write, it pushes authors to carefully frame their claims: is that really the canonically “correct” answer to this question?
I might summarize all that by saying that authors in the mnemonic medium must develop more formal theories of knowledge around their topic.