Aurra isn’t a Nightsister? Hounds Tooth isn’t a cargo ship?

That's... not really what it says. And they go into more detail in Dark Disciple.

Nightsister magic is Force use, drawing on both sides. The Nightsisters have a different relationship with the Force, therefore it manifests differently, and Dathomir is a powerful vergence in the Force, which lets them do some weird stuff. In the parlance of their Force tradition, they refer to their methods as magic, but they were aware of the Force as the same concept as identified by some other traditions.