let's imagine a different study. we instead compare AI-users and non-users on a Wechsler (IQ-adjacent) test.
overall, it would be surprising if AI usage impacted your Wechsler scores. someone has done this study and the impact is quite quite small. BUT. do we care? We don't use Wechsler scores for admissions, we don't use them for jobs, we don't use them for... are you getting it now? A Wechsler family test is measuring something real, just like a university exam measures something. But what do we USE them for? Wechsler and a typical university exam are, in some senses, EQUALLY vague in terms of their fitness for purpose for answering a question like, "should we hire this guy?"
Like there is an association between IQ and earnings but it is actually surprisingly small! There is an association with math education and earnings and it is also surprisingly small. And consider how many people get by just fine without using a single piece of math education once they have finished school - like what if maximizing your earnings isn't all that it is about? Are you getting it now?
The issue isn't the AI usage. I can find tests that are immune to AI usage. The issue is using tests for things that they are not designed for. We pick and choose, for some subtle but nonetheless pervasive cultural reasons, which tests we use for which purpose, and very frequently, not because they are calibrated for the chosen purpose. This is coming from someone who scores very well on all these tests, and have kids, so I have a very strong incentive to buy into the status quo, and I'm telling you: academic testing has been fucked up for a long, long time.