I feel that to learn something, writing it down is the best way to retain it.
You have limited attention capacity. So to utilise it the best you need to practice small chunk of the task at a time. Just like we eat in bites, not the whole plate at a time because we know our stomach can’t hold so much food.
But just like the eating we begin at the faster rate and end at a slower rate. Learning happens the same way. We start out with enthusiasm but, we can overdo it to the point of mental exhaustion.
Digest or learn in small chunks for better absorption and utilisation. When you just read, you tend to speed through the text. But when you write you take your time with every word.