I agree that a dirty vehicle doesn't mean anything, but there's far more to it than that. Look at those pictures. The guy can't even be troubled to cut the long tails off his wire ties. There's bodged stick-on weatherstripping everywhere, crudely made plywood doors, messy, homespun wiring, etc.
I bought a cruising sailboat like this once: a beautiful hull that someone had very inexpertly and crudely filled with dodgy cabinetry, tankage and wiring. Of course, it was good enough to sail to New Zealand and back, and in all fairness the guy actually sailed his boat rather than spending years piecing it all together. Still, I spent more time working on it than sailing it.
If the price were right and one were willing to take on a project....