He is unmoored.
The problem with having been raised on a ship by people who, no matter how good, could never be his mother is that Saf feels disconnected. It makes him a better thief and a worse brother, friend. He slips in and out of lives like rope slips through his fingers, practicing knots and ties he does not consciously produce.
The feel of being anchored frightens him, and he runs from it when the gravity of the crown and Sparks begin to pull him closer, steadying and terrifying simultaneously. In a new navy, far from home, he drifts.