Not to give you too much of a hard time... but this is the kind of stuff that gives ND fans a bad name. This is why other fan bases make the "must be grades" joke about us that wooly referred to in the Kimbrough thread.
There are tons of plausible answers here besides "grades" and absolutely zero evidence of any academic issue. The most plausible is the staff likes other prospects more than Biesel who is basically a consensus 3

who plays mediocre competition and doesn't have an elite offer list. He very well may earn an offer... most likely if we miss on Anzalone and other prospects. It's quite an imposition on the prospect to suggest academic issues without better rationale than you gave. There are plenty of real examples of academic issues (Perkins, Kimbrough, Byron Marshall, Anthony Standifer, etc. etc.) that lose legitimacy and start to sound like sour grapes when "must be grades" starts getting thrown around on every prospect without an offer.