What makes this interesting is that there is a small flaw in the reasoning.
It is a matter of abusing the tool, rather than using the tool.
Let's take a step back and examine the history of learning.
We can begin with the process of writing an essay as the assigned task.
Student One:
Disallowed from using any tools or outside resources. Only his own brain and knowledge base may be used. This creates high brain activity; as he engages the speculation and imagination portions in order to "invent" the necessary data to fill in the essay.
Result: The essay may be lengthy, but can include misinformation, inaccuracies, highly speculative conclusions, misspellings or grammar errors.
Student Two: Permitted to use encyclopedia's, local library; but no online tools.
This student will get more rest breaks between higher intense brain activity. He must engage his brain in research of data and knowledge retention and later employ the creative portions as he ties it together in the essay. His brain activity will be over all lower.
Result: They essay will contain more verifiable and accurate information, but may still include errors in data, due to misremembering data. Other small errors like grammar, spelling.
Student Three: Permitted a tutor (Editor), encyclopedia, library and online tools, excluding A.I.:
Brain activity will be lowered as the student relies on the editor/tutor to catch mistakes and offer suggestions, corrections or on-the-spot lessons on spelling, grammar and factual presentation. Student will spend equal time hitting the books as Student Two. Student has benefit of tutor.
Result: Best essay, yet. Cross checked with references, spelling and grammar errors caught. Get's an A+.
Student Four: Permitted A.I., online research resources, libraries, encyclopedias but banned from using a live tutor:
Student tells A.I. to write it for him.
Result: Good spelling and grammar. Over all factual, but contains a few grievous errors that can mislead.
We can all see the mistake that Student Four made. And having made that mistake... Student Four says, "Teach, look man, I messed up. Got lazy. But, I'd like to take another whack at this."
Teacher says, "Ok, I will allow you a second chance."
Student boots up the A.I. LLM and begins writing a draft. He begins with an essay skeleton that outlines the opening, central content and close. Once he has a rough draft, he posts a snippet of that portion to the A.I. It reviews it, then offers him revisions based of better word flow, readability, spelling and grammar.
Student cross checks the factual portions of the revisions using his other resources. According to Encyclopedia Britannica, the A.I. over simplified an aspect of WWII, creating factual ambiguity. The Student enhances that section, detailing relevant information. He resubmits this into the A.I., refining it further.
After re-reading the draft, he is satisfied and writes the complete draft.
Result: Best essay. Wins awards. Student runs for class president.
If tutors, assistants, resources and teachers created cognitive decline, then they would not have worked for the last... one hundred thousand years of human history.
The problem is laziness. Telling the A.I. to write it for you, instead of using it as a reference and tutor. The school bully picking on the nerd, only this nerd is not alive, has no lunch money, can't say 'no' and has no feelings or thoughts on the matter, at all.
But lower brain activity on an EEG?
Normal.
And if you hook up a smart doctor that knows time management and delegation in work priorities, you will get the same result. We even term it: "Work smarter, not harder."