There are turnovers and then there are turnovers. Meg Culmo has commented on good vs bad turnovers. If a player is being aggressive but just loses her handle or passes the ball with too much zip, Geno will grimace but not complain. But standing there with no idea what to do next, or throwing the ball into a crowd of defenders - or to the coach on the sideline with absolutely no defensive pressure - will earn a player a seat on the bench.
Geno has actually commented on Moriah's turnovers. He said in Jan-Feb (don't remember exactly) that she could be too passive and indecisive with the ball. For a program that depends so much on its point guard for direction, emotion and energy (think Jen, Rita, Sue, Renee...) having a kid that's unsure of herself at key points in the game is not going to help the team. Nor would throwing her to the wolves help the player's confidence. I know people wanted Geno to "season" Moriah by having her play more but it might have been counterproductive in the long run. If Moriah played 20 really bad minutes against an opponent, she would only learn that she's not ready to play at this level and it might affect her confidence going forward.
One of Geno's greatest gifts as a coach is his knowing his players as people. He knows who can take the sarcasm and verbal jabs and who needs a more paternal approach. If he thinks Moriah's confidence would suffer if she played at a certain point in the season or against a certain opponent, then he wouldn't play her. And it's not like he sits her and she doesn't know why. Shea, CD or Geno himself will tell her why and what she needs to do to avoid the benching. It's not a punishment - it's a learning experience.
Here's a link to an article where Kelly talks about Moriah's earlier-in-the-season tendency to hesitate.