Do you have data to back that up? Are you really trying to claim that there is no difference in outcomes from the average or below average graduate and summa cum laude?
That is moving the goal posts. No one claimed it is the sole predictor. The claim was that there is no relation at all. Your own links say their is a predictive relationship. Of course other factors matter, and may even be more important, but with all else equal, grades are positively correlated.
https://www.insidehighered.com/news/student-success/life-aft...
Actual study:
https://psycnet.apa.org/doiLanding?doi=10.1037%2Fapl0001212