"I didn't learn 'mind control'," 9S corrects primly. "This was something I was always able to do... to mechanical beings."

And the number of mechanical beings they encounter in any of the places they go to is a big zero, so of course he's never been able to use the very functions that define his entire model. So really, the only reason he hadn't used his hacking to solve more of their problems is because he couldn't.

"But... yeah, that's the plan. If I can't break someone else's mind control," though that would be the ideal outcome, "then I can at least make them less dangerous."