I can supply some anecdotally. I own two vehicles with reputations for running after neglected or minimal maintenance: a 1966 VW Beetle and a Land Rover.
The more correct way of characterising both would be that they will continue to run and function without ongoing maintenance (the proper level of which is way above a modern vehicle) until they break in a spectacular and often terminal way.
To attempt to answer your question, I think the general implication is that "old trucks" are designed for high maintenance intervals whereas Land Rovers, especially as used by the military, are designed to perform a function for short intervals with the long-term aid of a logistics chain.
I have a 2001 Nissan Xterra that's been sitting in my driveway for almost 4 years with a blown head gasket because of the combination of lack of spare time, other available vehicles that I could drive, and the complexity of disassembling the engine to remove the heads. The seats and hatch area are now full of engine parts and I still have to finish taking off the passenger side head.
Contrast that with my 1987 Toyota pickup: I would have had the entire job done in a weekend with time to spare.
The more correct way of characterising both would be that they will continue to run and function without ongoing maintenance (the proper level of which is way above a modern vehicle) until they break in a spectacular and often terminal way.
To attempt to answer your question, I think the general implication is that "old trucks" are designed for high maintenance intervals whereas Land Rovers, especially as used by the military, are designed to perform a function for short intervals with the long-term aid of a logistics chain.