I had to cover a huge set of knowledge fields from which ~65% I had zero experience with, neither theoretical nor practical.
The questions that were to be expected of course wouldn't go into too much detail, but the variance of possible questions made it necessary to gain a deeper understanding instead of just memorizing words (e.g. because used vocabulary can differ/overlap from domain to domain)
I've never heard of Luhman or his system, but always thought the knowledge contained in my Zettelkasten would make a great book and that the Zettelkasten's modular organization would make it very easy to parse the knowledge into whatever form you like.