It's sad but at the same time there is a sort of optimization that tends to occur each time the magic trick is rediscovered.
Often it is not possible to separate the technique from the man. Things like riding a bike or flying a helicopter come to mind. A lot of what makes a master good cannot be written down anywhere. There isn't anything tangible to actually lose.
How would you write a document that describes to someone how to ride a bike or dig holes efficiently? You could explain the principles and general ideas, but the apprentice is going to need to get scraped up a bit before they actually learn anything that matters. The apprentice willing to suffer repeated failure is where most of the heavy lifting occurs. The master is mostly a backstop to keep the apprentice alive.
You speak of tacit knowledge[1]
Worse is that they who have the knowledge don't realise that others don't know what they know, it's completely automatic and ingrained to the owner.
That's why this is speaking about apprentice and not about lectures in an university.
You don't need to write it down to pass the knowledge down to an apprentice.
Your bicycle case is a great example. People don't learn to ride a bike from a book. They receive in-person instruction of exactly the type the comment you're responding to was writing about.
> How would you write a document that describes to someone how to ride a bike or dig holes efficiently?
You don't. You put these people together for some years to work on stuff together, and a small percentage of this "intangible" feelings, knowledge and experiences you cannot write down somehow magically passes over to the other person.
Of course, the apprentice will still require their own repeated failures and uphill battle even getting close, but having someone who mastered the craft near you as you go through this, makes the whole process a hell of a lot faster.