Cars do NOT regularly go 200mph on the Autobahn. For one thing, very few cars can actually GO 200mph. For another, there are very few stretches of the A-bahn that are still unlimited, and they’re not all that long.
More likely, it’s “cars routinely do 200 KPH”, and some hit 250-270. I’ve been on the autobahn a few times on the non-limited stretches, and have seen the occasional big Merc sedan or Ferrari blast past at 130 or 140mph, but they’re rare. Most don’t go much over 90mph.
I went to Germany for vacation a couple of years ago and I would agree with your observation. I had the opportunity drive an American sports cars capable of doing 185 MPH on the autobahn. I took it to about 160MPH before I started to feel really uncomfortable. It gets rather loud with tire noise, engine noise, and air invading the cabin. In that car, relatively stress free driving seemed to be at about 120 MPH with very little traffic on the autobahn early Sunday morning.
Exceeding 140 MPH is not rare on a Sunday morning. I had to move over several times while doing +150 MPH. Those super cars are just amazing..