These kind of productivity tips always confuse me when they lack context of what the person writing is trying to do.
Like: Anki flashcards and spaced repetition. I see a lot of people advocating for them. I have never understood why because, in my personal experience, retaining lots of disconnected facts has never really been something I've needed to solve for. I do sort of see how it could work for rapid language learning (though I still think immersion, reading and writing are better than randomized vocabulary memorization, if you can take the time to do it that way), and I think I understand it in the context of fields like medicine where there's just a lot of facts you need to acquire, but people will advocate it for everything, and I just don't get it.
When I read a book, the process of reading it adds to the sum of my knowledge; I absorb the ideas, combine them with my own, and come to a new understanding of a topic. At that point, the book has accomplished its goal, for me.
But I acknowledge that's just how I read. I'm not an academic who might be later on finding myself needing to recall where I read something so I can cite it (although I find in general I can remember where I read certain things)... is that the use case here? What's the goal with building up an externalized knowledgeable?