Earlier quoted context omitted.
I too wonder the same thing. In addition to holding the concept in working memory for longer, writing being slower also leads to better refinement of the ideas as you write as the brain has more time to process the thought being written down.
what do you think is the difference between "being in the memory for longer" and "more time to process the thought"?
I meant the brain having more time to process the thought and thereby also actually processing it to refine it by connecting the dots better with the existing knowledge & understanding by recalling the latter too into the working memory from the long-term memory, as well as perhaps the working memory creating a stronger stimulus for the long-term memory to record better.
As an abstraction (which would not match how this actually works in the brain), merely having/holding a thought constant in the (working) memory for longer before transfering it to the long-term memory should not by itself lead to a better long-term memorization and recall, nor to a better understanding of the concepts involved. It could at best strengthen the working memory itself.
Please let me know if I misunderstood your question, if I am failing to answer it, and/or, if you think my understanding posited is not correct, accurate or complete. Would be happy to learn back and/or discuss further.