I think the German and American use of redline are different. I grew up in Germany and I can tell you that the 300se sold in Germany was expected to run continuously at near full throttle indefinitely on the autobahn. That's why Germans bought fast cars. To drive fast. To buy a 120mph car and only drive it at 70mph was inconceivable.
Redline in American cars is more an indication of where catastrophic failure can occur. I saw more than a few American cars run well below redline at continuous high speed on the autobahn grenade themselves because they weren't designed to operate at near full throttle at 5000rpm even though redline was indicated as 6000rpm.

Jorg