FWIW, Michael Sam was voted the SEC defensive player of the year yet many NFL scouts say he can't play and may only be mid-round pick. He had the right numbers in the right stats to get the award. Similarly, look at how many Heisman QB winners can't last at all in the NFL (Tebow) Awards are often given based on stats, and sometimes stats lie. I don't think Stef is the best off-ball defender on the team, nor is she the best shot blocker. You could argue she is the best rebounder but mostly because of her feet. She is also the best defensive coach on the court on the team. So when you look at her performance in totality, it is an easy case for her.
That all said, for the whole team to have only one scholarship player not get a post regular season award is pretty ridiculous and indicative of how bad some of the other starting fives are.