I kind of meant to point to system mastery in the sense that it's something valued at all.
As in, I've seen it said of some narrative-style games that it's not really necessary to understand the rules, it just helps things go more smoothly if you do. Some rules light systems are intended to be too simple and consistent for system mastery to be the interesting part. Some OSR systems, I suspect that confusion is an intentional part of the experience.
