I currently live in Germany and the technical inspections are all safety related, not cosmetic issues like rust.
Well, they can make a good case for issues to be "safety related". For any older car, rust *is* usually the deal breaker (as it reduces the integrity of the chassis - which is true, but I don't believe that it is indeed a cause for many traffic related injuries which would not happen otherwise). In fact, if your car is old enough to have historic plates, they are actually entitled to complain about cosmetic issues, as the historic plate mandates the car to be kept in a state "worth preserving". Ie, stuff like ("You need to repaint the valve cover in your engine bay as the paint on it became dated").
Regardless of that, I've had inspectors complain about tons of "safety" issues in my car or bikes over the years, including:
-Ripped seat cover ("passenger might be injured if a spring pokes out")
-Missing isolation cap on battery pole ("electical fire hazard")
-little skull shaped caps on tire valves ("not allowed")
-fan would not work on highest setting ("no guarantee of adequate cooling of passengers if going at high temperatures")
-Worn out seat
-Motorcycle not equipped with a steering column lock
-Motorcycle would engine would not auto-shut off when extending footstand (bike was made before these became standard, but that did not matter, had to retrofit)
(These are some examples - I've also met many inspectors much more reasonable then that, but still, I am convinced that the car industry is actually pushing for tighter inspections, as it will mean more new car sells. The car industry is the biggest arm of the german economy, and they do have a lot of power.)