I guess the point is the NCAA doesn't have the ability to do these investigations well and certainly not expediently. Maybe the easier shift is to give the athlete the benefit of the doubt and let them play/practice until it can be proven that they shouldn't be eligible. Diallo did nothing wrong but was punished by a slow and inept institution trying to do a job it is not equipped for.
If the NCAA wants to keep a list of shady high schools that might require additional vetting by universities, that's fine. But they clearly aren't able to carry out their duties as currently constructed so a change is needed.