2 scenarios (namely fixing the jumpgate and lost starbases) explicitly mention that whenever raiders reach the jumpgate, any damage applied can be mitigated with a shield roll.
Is it intentional that only these 2 scenarios offer this, while almost every other scenario with this specific raider movement mechanism do not have that mitigation roll? Was that rule perhaps simply forgotten (such as the "picking up a resource costs 1 movement" in the Abandoned rulebook)?
The individual scenarios are considered to be standalone games. So the "theme" is set on the scenario. You should not assume that each scenario is somehow connected/linked either mechanically or thematically with each other.
In one scenario you have shields and technology that can help you out under certain circumstances, in another scenario you do not.
Only the Legacy Campaign scenes are tied together under the same story/theme.