Having worked on a military base for years, they will go into a state of high alert over next to nothing. I think installation commanders simply figure that since everyone affected has already agreed to be part of a military installation with the ups and downs that brings, it's fine to err on the side of caution and activate security procedures for anything that comes up. It can be mildly annoying when you find out you're locked in because someone found something suspicious somewhere, but hey, you're working with the military. For the military, behaving as if they are under attack is part and parcel of the organization.

You don't alert the press until you're pretty damn sure, though. Military bases can already have stressed relationships with their communities and they don't need to be starting a panic over every change in the FPCON.