Absolutely true, and writing down 'cheat sheets' of such summaries was one of the most effective ways to learn. But I simply did not have the understanding yet, within 60 seconds of being presented new material, to be able to write a good summary of it. And at the same time also write a non-summary, in the likely case that things would not be clear from the summary alone when reviewing. And do all of this before the lecture moves on to the next thing that needs first understanding, then transcribing, then summarizing.