I don't see why cards need to be quite that simple. I generally take about 10-15 seconds for reviewing each card. A lot of my cards are why/how/what questions (typical examples: "Why are bras covariant?"/"How are Green's functions used in solving linear differential equations?"/"What is Q-Learning?") The problem with skipping memorization of concepts after having understood something is that two months later, you'll have forgotten those concepts. So, all that effort will have been in vain. I typically don't create much more than 10 cards a day, or maybe 20 on a day where I'm taking in a lot of information, and I typically have less than 50 cards to review. It's really not a huge time investment - especially if you're "busy".
> The problem with skipping memorization of concepts after having understood something is that two months later, you'll have forgotten those concepts.
The key realization, for me, is that conceptual understanding, intuitions, and key insights are themselves just pieces of information that can be memorized.
E.g.: Q: How to derive Bayes' Theorem? A: Write P(A and B) two different ways.
