Memorizing becomes easier after understanding. My guess is understanding things, not just what they mean, but how they work, or interact with other concepts, speeds up repetition quicker because that is what's firing when renewing it.
This is quite true; I feel this is the case with maths. Simple math, logic math is all fine, but higher maths and theorems I find very, very difficult to understand. Here this is one of the few areas where my memorizing techniques did not work well. Sure I can remember many things, but applying that knowledge is very different to just memorizing stuff.
Whether they're just for learning first principles first, and then a different set that are higher order connections between them.