Centipeetle isn't broken, she's corrupted. There's a difference.

Well, Rose was a gem, and her tears were used to heal other Gems. Yet it also works on organics. So his toy could make some sense. And not just immediate wounds either like a crack or broken bone, seeing as it worked on Connie's eyes too.

Granted, for all we know Rose might've only been able to heal Gems and Steven's works both ways because he's half-human. (Basically the same handwave they use for everything else.)