> If I forget everything I read, I can’t apply my knowledge to the problem at hand. I can’t transfer it.
Which is true, but I'm not really sure your solution is the best way to solve this problem. When you learn react, you are not trying to memorize the full book, you are trying to learn to be able to code in react which is a really different thing. The world champion of french Scrabble doesn't speak french [1]
To me you are over engineering the learning process. Learning benefits a lot from forgetting, there is no point trying to memorize a full book so that's normal to forget most of it
There are benefits from memorizing a full book but not for the case you are showing as an example (learning React or js)
[1] https://www.npr.org/sections/thetwo-way/2015/07/21/424980378...