> But isn’t the point of writing an essay is the quality of the essay

Most of the things you write in an educational context are about learning, not about producing something of value. Productivity in a learning context is usually the wrong lens. The same thing is true IMO for learning on the job, where it is typically expected that productivity will initially be low while experience is low, but should increase over time.

That may be true if this was measuring an English class. But the experiment was just writing essays, there were no other instruction other write an essay either with no tools, ChatGPT, or a search engine. That is the only variable was tool or without tool.