Comment by devmor
Your question is answered by the study abstract.
> Over four months, LLM users consistently underperformed at neural, linguistic, and behavioral levels. These results raise concerns about the long-term educational implications of LLM reliance and underscore the need for deeper inquiry into AI's role in learning.
But it's not that they "underperformed" at life in general - they underperformed when assessed on various aspects of the task that they weren't practicing. To me it's as if they ran a trial where one group played basketball, while another were acting as referees - of course that when tested on ball control, those who were dribbling and throwing would do better, but it tells us nothing about how those acting as referees performed at their thing.