> Fractions is exactly an area of mathematics where I learned by understanding the concept and how it was represented and then would use that understanding to re-reason the procedures I had a hard time remembering.
Sure, I did that plenty too, but that doesn't refute the point that memorization is core to understanding mathematics, it's just a specific kind of memorization that results maximal flexibility for minimal state retention. All you're claiming is that you memorized some core axioms/primitives and the procedures that operate on them, and then memorized how higher-level concepts are defined in terms of that core. I go into more detail of the specifics here:
https://news.ycombinator.com/item?id=40669585
I agree that this is a better way to memorize mathematics, eg. it's more parsimonious than memorizing lots of shortcuts. We call this type of memorizing "understanding" because it's arguably the most parsimonious approach, requiring the least memory, and machine learning has persuasively argued IMO that compression is understanding [1].
[1] https://philpapers.org/rec/WILUAC-2