Does articulating your reasoning about a topic produce understanding that passive reading simply cannot?

I can read an article on a complex topic and feel like I understand it well, but the moment I try to write out my own reasoning — to actually justify a position — I discover I understood far less than I thought. The articulation reveals something the reading hid. Is this a documented epistemological phenomenon? Is the felt sense of understanding after passive reading actually a different cognitive state than understanding-demonstrated-through-reasoning, or are they the same thing measured differently?