How would anyone know if the kids are borderline? You can meet the minimum requirements for NCAA eligibility and yet not be able to make it academically at Duke if you're taking the same level courses as the average student there. If they stay only a year or two nobody knows how good or bad they were academically.
Georgetown was a good example of a school that took some real gems. . Victor Page was a great player but only lasted two years purportedly because they ran out of ways to keep him eligible. Same with Michael Graham, the guy who forced the NCAA into coming up with the fighting rule. He played one year and drew blood in two games and was Ewing's protector. Graham took care of anybody that got near Ewing so he could operate freely. They won their only championship that year and Graham was gone after that one year, due to academic eligibility issues according to Wikipedia. They used him, got what they wanted and didn't need him anymore. They're Jesuits: the end justifies the means.
You know which kids are borderline while they're in high school. We're not talking about what they do in college...that doesn't matter other than staying out of the NCAAs cross hairs. Everyone but UCONN's grades are fudged.
The kids who are borderline recruits are a
struggle to get eligible. Often not cleared til halfway through their first year. Usually need to take extra courses (cause they've gone to diploma mills), retake qualifying exams (with serious preparatory help), and in some cases, get grades fudged.
Duke is different because they pretty much have their pick of the Top 25. They can pick and choose and avoid the 'land mine' kids.