I came across one of these for the first time today. I cored all the ships and sentries. I even found the loot box on the destroyed shipyard . But the shipyard's core was labeled as indestructible and there was no obvious "congrats, you are done, here is a reward cache". Is that how it ends or was there something I missed?

I'll add that there is a mission associated with the sector that has not been started, but I gather not all sector missions are meaningful.