I think they're touching on multiple things that typically happens between an apprentice and master, not just tacit knowledge. Also implicit learning, procedural / nondeclarative memory, expert intuition and metacognitive feelings, all very hard to quantify into a written document, but put two people together where one learns from the other, and all these somehow gets transferred over time.

"Always two, there are. No more. No less. A Master and an apprentice."

Sounds great, looking into it, maybe less great. Apparently from Star Wars, about the Sith :)

> The Rule of Two did away with Sith Academies. From your very first steps into the Dark Side, you work with your Master and only your Master. You are not responsible to other Dark Side users. You are not expected to delve into the secrets of the Dark Side and give that knowledge to Force-users other than your Master (or hide it from him). You're expected to do what you can to keep other potential Force-wielders from usurping your position, including kill them. You're expected to learn what your Master teaches you, but also to hide from him in order to overtake him.

Ideally your real-life experience with apprenticeship has been/will be slightly different than this!

There's nothing implied about tacit knowledge being knowledge that you don't know others don't have. For instance in chess mastery, one is fully aware that you simply see the board in a different way. It's not like you're aloof of your own 'advantage', but then in lessons you work to gradually, step by step, instill such in the student. Some of the most successful teachers are those who themselves learned the game a bit later than average, enabling them to draw more heavily on their own path. For instance Mark Dvoretsky only earned the IM title when he was 28!

28? You make it sound like he was 90!

haha, well his methods, that live on after he's gone, are a big part of the reason people are now making GM at 12.

It's unclear whether these sort of players will do as good a job at handing down their knowledge though. Think about how little you remember, in much detail at least, about stuff before you were 12 - and now imagine you were already master strength by then, let alone a grandmaster. I'm a later starter and can still vividly remember when I barely knew how the pieces moved, and I think that gives me a huge edge over most players in terms of teaching.