Well, data in Inara (or any other of the external tools) is provided by those players who are running one of the update tools (like EDMC or EDDiscovery) while playing. So the carrier data was accurate the last time a player running one of these tools passed through that system - which may have been weeks ago.
But there is also at least one permanent station in one of the Guardian ruin systems. On the other hand, neither a second SRV nor point defense are actually necessary - we collected artifacts, materials and blueprints before someone discovered that a ship's PD could provide protection from the sentinels' missiles.