The ergos seem strange to me also, as if the Germans produced the rifles for shorter people.
IF you're talking about the HK 91 design, remember its a semi auto version of a military rifle. And its a long known fact that larger people can adapt and handle a rifle that's a little too short better then shorter people can manage a rifle that's a little too long.
Its a "one size fits all, well enough" thing. And, I think the average European is still a bit shorter than the average American overall, as well.
the other thing is that German designers often follow a slightly different school of thought than US designers. Generally speaking, US designers usually make it so all the major controls are operated by the shooting (trigger) hand (usually the right hand) and are within easy reach or can be reached with a slight shift of the hand.
Several European (primarily German) designs are apparently intended for the non trigger hand to operate some controls. Such as the safety or operating handle. Some of them have the safety where it simply cannot be reached with the shooting hand in the firing position.
One can see this idea in WWII holsters most easily. The US holster for the 1911A1 was a flap holster but still a fairly rapid draw. The German holsters were "luggage cases" some even had buckles keeping them securely closed.
A German once explained this to me, its the differnce in our "mindsets". An American soldier is a cowboy, who thinks he needs to draw his pistol rapidly at need and use it. A German soldier will draw his pistol before going into combat (so the speed and ease of the draw doesn't matter) and will have it in his hand when he needs it.
Different way of looking at it, we both thought the other side was crazy...Still, they think certain things are right, and proper and build their stuff to work, their way...
Does remind me of a "joke" that probably was a real situation....an American is looking over a high end German sports car, and makes a comment about the lack of cup holders...
to which the German engineer indignantly replies,
"das Auto is fur DRIVING, not fur Drinking!"