Even heavy checks don't typically need an airtest - in the days when I was hands-on with such activities, the only such flights that I can recall were very occasional ones where a fault couldn't be reproduced on the ground and a memorable one (which I hitched a ride on) after a tailplane was replaced on a Viscount (which, for reasons I never understood, involved doing stalls and engine shutdowns, probably just because the crew couldn't resist the opportunity and I certainly wasn't about to shop them 
).
i think you were very brave/naive to have willingly gone in a test-flight of an aircraft after a tailplane replacement!
Back to the civilians working on Military aircraft, in general i'm surprised that so many militaries allow their assets to be out of their sight/security notwithstanding Marshalls reputation and abilities. I get the economics and efficiency of such arrangements, but not the security issues/risks.