This research is based on people being given 20 minutes to research and write an "essay"? (Or, in the Brain only case, write an "essay" without doing any research.)

How is that not utter garbage? You're comparing text that is barely more than a forum comment, and noticing that people who spend the short time thinking and writing are engaging in different activity from people who spend the time using a research tools and different activity from people whow spend the time asking an AI (and waiting for it) to generate content.