Yeah, I get that too. You could look at differences in academic standards and admissions and say some discrepancy is accounted for there. But not nearly enough, I'd wager. You could look at two schools like LSU and Florida and say due to admission requirements and school policies, it's easier for a kid to get into--and stay in--LSU than it is Florida. Unfortunately I don't think there's difference in practice. You can hear Gator players interviewed where they sound every bit as unqualified to be there as anybody LSU has. I'm not picking on those schools, just using them for examples. I haven't seen the report you're referring to, but I don't doubt it.
While that's been a gradual decline in "student-athletes," I think it still belongs in a separate bin than the NIL stuff. Even if these guys aren't qualified to be at the university, they were still sold on the program and something inside them made them want to represent the university in athletics, even if they don't meet its academic standards. I can't help but think NIL will ultimately erode that as well. I guess what I'm saying is I see a difference between a dumb, loyal player with school spirit, and a dumb, take-me-to-the-highest-bidder player.
Granted, not everyone who leaves is disloyal or lacks school spirit. There have always been transfers for various reasons, as you pointed out with Burrow being an example. From what's filtered through the grapevine, we're told that Burrow never stopped being a Buckeye on the inside, and I don't mean that to question his love or loyalty to LSU, only that he didn't sour on his original school, he just saw an opportunity and made a choice, but deep inside he may have preferred that he could've taken that same journey in the scarlet and grey. But transfers like that, or any from the previous era, were much more rare than what we're getting now, and the difference in motive in clear.