Do we really have to get into the realms of fantasy?
Why would any "black" projects be stored at a civilian operation, especially when Edwards, Palmdale and the bases on the Nellis ranges, all which are used for secret and semi secret projects, are so close in terms of flying time? All have much better security than Pinal. Even Davis Monthan is more secure in certain areas.
Pinal is regularly visited by nationals of many different countries calling to visit to pick/deliver up aircraft on ferry or to see aircraft with a view to lease/purchase - just what the Pentagon and DoD would want for somewhere they sometimes store black aircraft.
The airfield is not subject to any overfly restrictions and visitors, like myself, can still get photo access if they know the right person.
The reason Pinal is so security conscious is that the value of the aircraft stored is higher, in terms of parts,
than that of the whole airframes - and many of the aircraft beung "parted out" become vulnerable to theft.
There is a vast open area, that if not secured at ground level, could be the subject of pilfering, or just stupid vandalism and the airfield is, after all, private property.