With apologies to JS for treading on his territory, law is often a matter of interpretation. My particular pet peeve is the Supreme Court interpreting that corporations are individuals, an oxymoron that has had atrocious consequences, but I digress.
No one debates that what happened at UNC was academic fraud. If only student athletes took the courses most likely anyone, even the NCAA, would interpret the purpose of academic fraud as eligibility fraud, making athletes eligible who otherwise would not be. Since some students took the "classes" who were not athletes, this now makes it a matter of interpretation whether the eligibility fraud was the intent. Several lines of evidence suggest that eligibility fraud was still the intent, with the nonathletes providing cover. There certainly is precedence for the NCAA sanctioning eligibility fraud, but from the evidence the NCAA interpreted that this was not conclusively the purpose of the academic fraud.
A matter of interpretation. Whether the interpretation by the NCAA was correct or what was the motivation for the interpretation is left for folks to ponder, or not. Yet had the NCAA interpreted from the evidence that eligibility fraud was the intent of the academic fraud, then that would have opened the door for NCAA sanctions.